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	$216.57	13.408%	$245.6077	$245.61	$245.60	$245.60
Purchase #2	$9.70	11.645%	$10.8296	$10.83	$10.85	$10.80
Purchase #3	$74.59	5.136%	$78.4209	$78.42	$78.40	$78.40
Purchase #4	$82.82	7.494%	$89.0265	$89.03	$89.05	$89.00
Purchase #5	$89.82	3.151%	$92.6502	$92.65	$92.65	$92.70
Purchase #6	$142.60	11.263%	$158.661	$158.66	$158.65	$158.70
Purchase #7	$193.65	5.401%	$204.109	$204.11	$204.10	$204.10
7 purchase totals =	$809.75		$879.3049	$879.31	$879.30	$879.30