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	$244.91	3.343%	$253.0973	$253.10	$253.10	$253.10
Purchase #2	$193.88	12.152%	$217.4403	$217.44	$217.45	$217.40
Purchase #3	$85.70	3.179%	$88.4244	$88.42	$88.40	$88.40
Purchase #4	$107.60	3.437%	$111.2982	$111.30	$111.30	$111.30
Purchase #5	$196.48	7.594%	$211.4007	$211.40	$211.40	$211.40
Purchase #6	$75.66	9.573%	$82.9029	$82.90	$82.90	$82.90
Purchase #7	$56.61	3.618%	$58.6581	$58.66	$58.65	$58.70
7 purchase totals =	$960.84		$1,023.2219	$1,023.22	$1,023.20	$1,023.20