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	$118.29	7.414%	$127.06	$127.06	$127.05	$127.10
Purchase #2	$181.81	4.736%	$190.4205	$190.42	$190.40	$190.40
Purchase #3	$10.67	3.381%	$11.0308	$11.03	$11.05	$11.00
Purchase #4	$125.99	4.186%	$131.2639	$131.26	$131.25	$131.30
Purchase #5	$92.77	4.300%	$96.7591	$96.76	$96.75	$96.80
Purchase #6	$77.88	10.348%	$85.939	$85.94	$85.95	$85.90
Purchase #7	$154.46	11.614%	$172.399	$172.40	$172.40	$172.40
7 purchase totals =	$761.87		$814.8723	$814.87	$814.85	$814.90