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	$33.96	10.630%	$37.5699	$37.57	$37.55	$37.60
Purchase #2	$213.58	9.216%	$233.2635	$233.26	$233.25	$233.30
Purchase #3	$248.47	8.111%	$268.6234	$268.62	$268.60	$268.60
Purchase #4	$145.99	7.453%	$156.8706	$156.87	$156.85	$156.90
Purchase #5	$45.90	3.532%	$47.5212	$47.52	$47.50	$47.50
Purchase #6	$130.32	10.150%	$143.5475	$143.55	$143.55	$143.50
Purchase #7	$191.51	7.755%	$206.3616	$206.36	$206.35	$206.40
7 purchase totals =	$1,009.73		$1,093.7577	$1,093.75	$1,093.65	$1,093.80