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	$87.33	7.277%	$93.685	$93.69	$93.70	$93.70
Purchase #2	$207.55	12.436%	$233.3609	$233.36	$233.35	$233.40
Purchase #3	$134.72	12.335%	$151.3377	$151.34	$151.35	$151.30
Purchase #4	$245.29	9.368%	$268.2688	$268.27	$268.25	$268.30
Purchase #5	$85.26	5.642%	$90.0704	$90.07	$90.05	$90.10
Purchase #6	$249.68	7.573%	$268.5883	$268.59	$268.60	$268.60
Purchase #7	$64.40	4.812%	$67.4989	$67.50	$67.50	$67.50
7 purchase totals =	$1,074.23		$1,172.8100	$1,172.82	$1,172.80	$1,172.90