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	$146.73	3.526%	$151.9037	$151.90	$151.90	$151.90
Purchase #2	$178.99	4.637%	$187.2898	$187.29	$187.30	$187.30
Purchase #3	$130.93	9.719%	$143.6551	$143.66	$143.65	$143.70
Purchase #4	$96.58	11.332%	$107.5244	$107.52	$107.50	$107.50
Purchase #5	$205.50	13.751%	$233.7583	$233.76	$233.75	$233.80
Purchase #6	$40.88	10.743%	$45.2717	$45.27	$45.25	$45.30
Purchase #7	$130.72	9.537%	$143.1868	$143.19	$143.20	$143.20
7 purchase totals =	$930.33		$1,012.5898	$1,012.59	$1,012.55	$1,012.70