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	$61.88	12.865%	$69.8409	$69.84	$69.85	$69.80
Purchase #2	$91.57	9.753%	$100.5008	$100.50	$100.50	$100.50
Purchase #3	$43.58	5.259%	$45.8719	$45.87	$45.85	$45.90
Purchase #4	$67.85	3.412%	$70.165	$70.17	$70.15	$70.20
Purchase #5	$127.31	7.538%	$136.9066	$136.91	$136.90	$136.90
Purchase #6	$202.47	13.156%	$229.107	$229.11	$229.10	$229.10
Purchase #7	$91.91	8.128%	$99.3804	$99.38	$99.40	$99.40
7 purchase totals =	$686.57		$751.7726	$751.78	$751.75	$751.80