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	$91.61	8.314%	$99.2265	$99.23	$99.25	$99.20
Purchase #2	$142.39	8.123%	$153.9563	$153.96	$153.95	$154.00
Purchase #3	$221.91	13.549%	$251.9766	$251.98	$252.00	$252.00
Purchase #4	$178.36	3.591%	$184.7649	$184.76	$184.75	$184.80
Purchase #5	$250.44	9.285%	$273.6934	$273.69	$273.70	$273.70
Purchase #6	$148.91	11.122%	$165.4718	$165.47	$165.45	$165.50
Purchase #7	$133.43	6.774%	$142.4685	$142.47	$142.45	$142.50
7 purchase totals =	$1,167.05		$1,271.5580	$1,271.56	$1,271.55	$1,271.70