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	$202.47	10.267%	$223.2576	$223.26	$223.25	$223.30
Purchase #2	$116.36	10.699%	$128.8094	$128.81	$128.80	$128.80
Purchase #3	$70.49	3.388%	$72.8782	$72.88	$72.90	$72.90
Purchase #4	$133.78	12.792%	$150.8931	$150.89	$150.90	$150.90
Purchase #5	$234.40	7.874%	$252.8567	$252.86	$252.85	$252.90
Purchase #6	$55.79	8.141%	$60.3319	$60.33	$60.35	$60.30
Purchase #7	$94.84	4.498%	$99.1059	$99.11	$99.10	$99.10
7 purchase totals =	$908.13		$988.1328	$988.14	$988.15	$988.20