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	$199.37	6.232%	$211.7947	$211.79	$211.80	$211.80
Purchase #2	$55.45	7.106%	$59.3903	$59.39	$59.40	$59.40
Purchase #3	$127.75	8.359%	$138.4286	$138.43	$138.45	$138.40
Purchase #4	$158.74	6.347%	$168.8152	$168.82	$168.80	$168.80
Purchase #5	$32.81	10.102%	$36.1245	$36.12	$36.10	$36.10
Purchase #6	$247.37	13.713%	$281.2918	$281.29	$281.30	$281.30
Purchase #7	$156.29	11.541%	$174.3274	$174.33	$174.35	$174.30
7 purchase totals =	$977.78		$1,070.1725	$1,070.17	$1,070.20	$1,070.10