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	$97.42	12.249%	$109.353	$109.35	$109.35	$109.40
Purchase #2	$65.44	12.349%	$73.5212	$73.52	$73.50	$73.50
Purchase #3	$23.51	8.115%	$25.4178	$25.42	$25.40	$25.40
Purchase #4	$70.75	11.512%	$78.8947	$78.89	$78.90	$78.90
Purchase #5	$35.36	7.747%	$38.0993	$38.10	$38.10	$38.10
Purchase #6	$38.55	10.598%	$42.6355	$42.64	$42.65	$42.60
Purchase #7	$55.40	10.359%	$61.1389	$61.14	$61.15	$61.10
7 purchase totals =	$386.43		$429.0604	$429.06	$429.05	$429.00