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	$198.52	6.129%	$210.6873	$210.69	$210.70	$210.70
Purchase #2	$211.88	12.161%	$237.6467	$237.65	$237.65	$237.60
Purchase #3	$39.39	3.808%	$40.89	$40.89	$40.90	$40.90
Purchase #4	$107.42	11.840%	$120.1385	$120.14	$120.15	$120.10
Purchase #5	$158.78	5.374%	$167.3128	$167.31	$167.30	$167.30
Purchase #6	$162.31	11.219%	$180.5196	$180.52	$180.50	$180.50
Purchase #7	$105.43	5.380%	$111.1021	$111.10	$111.10	$111.10
7 purchase totals =	$983.73		$1,068.2970	$1,068.30	$1,068.30	$1,068.20