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	$191.60	9.637%	$210.0645	$210.06	$210.05	$210.10
Purchase #2	$190.46	6.801%	$203.4132	$203.41	$203.40	$203.40
Purchase #3	$47.82	4.203%	$49.8299	$49.83	$49.85	$49.80
Purchase #4	$223.46	3.347%	$230.9392	$230.94	$230.95	$230.90
Purchase #5	$134.81	6.168%	$143.1251	$143.13	$143.15	$143.10
Purchase #6	$139.72	3.288%	$144.314	$144.31	$144.30	$144.30
Purchase #7	$83.86	9.270%	$91.6338	$91.63	$91.65	$91.60
7 purchase totals =	$1,011.73		$1,073.3197	$1,073.31	$1,073.35	$1,073.20