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	$224.91	9.869%	$247.1064	$247.11	$247.10	$247.10
Purchase #2	$199.44	6.752%	$212.9062	$212.91	$212.90	$212.90
Purchase #3	$79.27	4.588%	$82.9069	$82.91	$82.90	$82.90
Purchase #4	$168.99	9.580%	$185.1792	$185.18	$185.20	$185.20
Purchase #5	$138.76	10.779%	$153.7169	$153.72	$153.70	$153.70
Purchase #6	$120.26	6.352%	$127.8989	$127.90	$127.90	$127.90
Purchase #7	$161.96	6.352%	$172.2477	$172.25	$172.25	$172.20
7 purchase totals =	$1,093.59		$1,181.9622	$1,181.98	$1,181.95	$1,181.90