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	$150.97	3.261%	$155.8931	$155.89	$155.90	$155.90
Purchase #2	$152.33	6.777%	$162.6534	$162.65	$162.65	$162.70
Purchase #3	$240.27	13.139%	$271.8391	$271.84	$271.85	$271.80
Purchase #4	$50.74	9.667%	$55.645	$55.65	$55.65	$55.60
Purchase #5	$240.98	5.776%	$254.899	$254.90	$254.90	$254.90
Purchase #6	$176.49	3.154%	$182.0565	$182.06	$182.05	$182.10
Purchase #7	$72.56	5.418%	$76.4913	$76.49	$76.50	$76.50
7 purchase totals =	$1,084.34		$1,159.4774	$1,159.48	$1,159.50	$1,159.50