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	$197.85	6.298%	$210.3106	$210.31	$210.30	$210.30
Purchase #2	$66.26	8.271%	$71.7404	$71.74	$71.75	$71.70
Purchase #3	$155.73	10.719%	$172.4227	$172.42	$172.40	$172.40
Purchase #4	$81.46	10.157%	$89.7339	$89.73	$89.75	$89.70
Purchase #5	$22.89	12.616%	$25.7778	$25.78	$25.80	$25.80
Purchase #6	$101.88	11.749%	$113.8499	$113.85	$113.85	$113.80
Purchase #7	$71.27	5.428%	$75.1385	$75.14	$75.15	$75.10
7 purchase totals =	$697.34		$758.9738	$758.97	$759.00	$758.80