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	$74.36	10.413%	$82.1031	$82.10	$82.10	$82.10
Purchase #2	$126.62	11.562%	$141.2598	$141.26	$141.25	$141.30
Purchase #3	$201.99	8.139%	$218.43	$218.43	$218.45	$218.40
Purchase #4	$118.59	7.712%	$127.7357	$127.74	$127.75	$127.70
Purchase #5	$142.35	9.304%	$155.5942	$155.59	$155.60	$155.60
Purchase #6	$165.30	3.184%	$170.5632	$170.56	$170.55	$170.60
Purchase #7	$224.41	11.465%	$250.1386	$250.14	$250.15	$250.10
7 purchase totals =	$1,053.62		$1,145.8246	$1,145.82	$1,145.85	$1,145.80