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	$190.81	6.544%	$203.2966	$203.30	$203.30	$203.30
Purchase #2	$53.79	7.573%	$57.8635	$57.86	$57.85	$57.90
Purchase #3	$209.66	10.351%	$231.3619	$231.36	$231.35	$231.40
Purchase #4	$147.73	6.147%	$156.811	$156.81	$156.80	$156.80
Purchase #5	$196.33	5.377%	$206.8867	$206.89	$206.90	$206.90
Purchase #6	$49.58	5.140%	$52.1284	$52.13	$52.15	$52.10
Purchase #7	$172.72	7.355%	$185.4236	$185.42	$185.40	$185.40
7 purchase totals =	$1,020.62		$1,093.7717	$1,093.77	$1,093.75	$1,093.80