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	$171.45	5.741%	$181.2929	$181.29	$181.30	$181.30
Purchase #2	$7.54	6.324%	$8.0168	$8.02	$8.00	$8.00
Purchase #3	$91.66	8.165%	$99.144	$99.14	$99.15	$99.10
Purchase #4	$143.87	5.679%	$152.0404	$152.04	$152.05	$152.00
Purchase #5	$144.83	5.341%	$152.5654	$152.57	$152.55	$152.60
Purchase #6	$130.97	6.286%	$139.2028	$139.20	$139.20	$139.20
Purchase #7	$242.33	7.740%	$261.0863	$261.09	$261.10	$261.10
7 purchase totals =	$932.65		$993.3486	$993.35	$993.35	$993.30