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	$202.28	10.420%	$223.3576	$223.36	$223.35	$223.40
Purchase #2	$155.72	4.535%	$162.7819	$162.78	$162.80	$162.80
Purchase #3	$11.69	6.473%	$12.4467	$12.45	$12.45	$12.40
Purchase #4	$158.50	13.312%	$179.5995	$179.60	$179.60	$179.60
Purchase #5	$192.33	4.461%	$200.9098	$200.91	$200.90	$200.90
Purchase #6	$54.70	9.376%	$59.8287	$59.83	$59.85	$59.80
Purchase #7	$79.54	13.489%	$90.2692	$90.27	$90.25	$90.30
7 purchase totals =	$854.76		$929.1934	$929.20	$929.20	$929.20