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	$52.87	9.268%	$57.77	$57.77	$57.75	$57.80
Purchase #2	$41.41	7.215%	$44.3977	$44.40	$44.40	$44.40
Purchase #3	$55.61	10.310%	$61.3434	$61.34	$61.35	$61.30
Purchase #4	$40.94	6.337%	$43.5344	$43.53	$43.55	$43.50
Purchase #5	$141.82	6.166%	$150.5646	$150.56	$150.55	$150.60
Purchase #6	$77.61	3.369%	$80.2247	$80.22	$80.20	$80.20
Purchase #7	$181.63	7.634%	$195.4956	$195.50	$195.50	$195.50
7 purchase totals =	$591.89		$633.3304	$633.32	$633.30	$633.30