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	$211.94	3.548%	$219.4596	$219.46	$219.45	$219.50
Purchase #2	$222.25	5.408%	$234.2693	$234.27	$234.25	$234.30
Purchase #3	$64.74	10.697%	$71.6652	$71.67	$71.65	$71.70
Purchase #4	$58.71	12.220%	$65.8844	$65.88	$65.90	$65.90
Purchase #5	$56.49	5.564%	$59.6331	$59.63	$59.65	$59.60
Purchase #6	$247.75	10.489%	$273.7365	$273.74	$273.75	$273.70
Purchase #7	$224.99	10.631%	$248.9087	$248.91	$248.90	$248.90
7 purchase totals =	$1,086.87		$1,173.5568	$1,173.56	$1,173.55	$1,173.60