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	$185.70	8.769%	$201.984	$201.98	$202.00	$202.00
Purchase #2	$237.36	8.814%	$258.2809	$258.28	$258.30	$258.30
Purchase #3	$140.66	4.570%	$147.0882	$147.09	$147.10	$147.10
Purchase #4	$50.92	3.147%	$52.5225	$52.52	$52.50	$52.50
Purchase #5	$53.33	11.847%	$59.648	$59.65	$59.65	$59.60
Purchase #6	$195.55	7.251%	$209.7293	$209.73	$209.75	$209.70
Purchase #7	$107.30	4.288%	$111.901	$111.90	$111.90	$111.90
7 purchase totals =	$970.82		$1,041.1539	$1,041.15	$1,041.20	$1,041.10