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	$209.51	10.399%	$231.2969	$231.30	$231.30	$231.30
Purchase #2	$56.43	13.483%	$64.0385	$64.04	$64.05	$64.00
Purchase #3	$181.69	9.461%	$198.8797	$198.88	$198.90	$198.90
Purchase #4	$89.76	6.379%	$95.4858	$95.49	$95.50	$95.50
Purchase #5	$99.25	10.351%	$109.5234	$109.52	$109.50	$109.50
Purchase #6	$229.32	6.540%	$244.3175	$244.32	$244.30	$244.30
Purchase #7	$97.95	13.439%	$111.1135	$111.11	$111.10	$111.10
7 purchase totals =	$963.91		$1,054.6553	$1,054.66	$1,054.65	$1,054.60