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	$198.35	5.453%	$209.166	$209.17	$209.15	$209.20
Purchase #2	$244.62	11.734%	$273.3237	$273.32	$273.30	$273.30
Purchase #3	$74.74	9.727%	$82.01	$82.01	$82.00	$82.00
Purchase #4	$123.48	5.568%	$130.3554	$130.36	$130.35	$130.40
Purchase #5	$242.76	4.851%	$254.5363	$254.54	$254.55	$254.50
Purchase #6	$98.50	10.553%	$108.8947	$108.89	$108.90	$108.90
Purchase #7	$83.54	12.816%	$94.2465	$94.25	$94.25	$94.20
7 purchase totals =	$1,065.99		$1,152.5326	$1,152.54	$1,152.50	$1,152.50