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	$74.63	4.790%	$78.2048	$78.20	$78.20	$78.20
Purchase #2	$235.55	4.572%	$246.3193	$246.32	$246.30	$246.30
Purchase #3	$247.61	4.557%	$258.8936	$258.89	$258.90	$258.90
Purchase #4	$143.62	6.231%	$152.569	$152.57	$152.55	$152.60
Purchase #5	$39.34	7.174%	$42.1623	$42.16	$42.15	$42.20
Purchase #6	$132.76	4.157%	$138.2788	$138.28	$138.30	$138.30
Purchase #7	$210.94	5.315%	$222.1515	$222.15	$222.15	$222.20
7 purchase totals =	$1,084.45		$1,138.5793	$1,138.57	$1,138.55	$1,138.70