Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.98	13.406%	$181.4269	$181.43	$181.45	$181.40
Purchase #2	$170.92	10.729%	$189.258	$189.26	$189.25	$189.30
Purchase #3	$164.32	11.456%	$183.1445	$183.14	$183.15	$183.10
Purchase #4	$107.74	3.804%	$111.8384	$111.84	$111.85	$111.80
Purchase #5	$240.73	9.345%	$263.2262	$263.23	$263.25	$263.20
Purchase #6	$127.73	3.426%	$132.106	$132.11	$132.10	$132.10
Purchase #7	$170.93	8.745%	$185.8778	$185.88	$185.90	$185.90
7 purchase totals =	$1,142.35		$1,246.8778	$1,246.89	$1,246.95	$1,246.80