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	$125.25	5.170%	$131.7254	$131.73	$131.75	$131.70
Purchase #2	$165.46	9.600%	$181.3442	$181.34	$181.35	$181.30
Purchase #3	$222.52	8.771%	$242.0372	$242.04	$242.05	$242.00
Purchase #4	$78.50	4.857%	$82.3127	$82.31	$82.30	$82.30
Purchase #5	$77.48	13.642%	$88.0498	$88.05	$88.05	$88.00
Purchase #6	$62.41	13.282%	$70.6993	$70.70	$70.70	$70.70
Purchase #7	$154.33	13.605%	$175.3266	$175.33	$175.35	$175.30
7 purchase totals =	$885.95		$971.4952	$971.50	$971.55	$971.30