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	$97.86	12.347%	$109.9428	$109.94	$109.95	$109.90
Purchase #2	$243.83	4.558%	$254.9438	$254.94	$254.95	$254.90
Purchase #3	$55.93	7.170%	$59.9402	$59.94	$59.95	$59.90
Purchase #4	$23.79	4.632%	$24.892	$24.89	$24.90	$24.90
Purchase #5	$94.63	6.480%	$100.762	$100.76	$100.75	$100.80
Purchase #6	$106.91	7.762%	$115.2084	$115.21	$115.20	$115.20
Purchase #7	$120.55	4.756%	$126.2834	$126.28	$126.30	$126.30
7 purchase totals =	$743.50		$791.9726	$791.96	$792.00	$791.90