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	$243.85	6.593%	$259.927	$259.93	$259.95	$259.90
Purchase #2	$67.67	6.140%	$71.8249	$71.82	$71.80	$71.80
Purchase #3	$155.64	9.512%	$170.4445	$170.44	$170.45	$170.40
Purchase #4	$54.57	7.768%	$58.809	$58.81	$58.80	$58.80
Purchase #5	$243.87	10.479%	$269.4251	$269.43	$269.45	$269.40
Purchase #6	$80.60	10.464%	$89.034	$89.03	$89.05	$89.00
Purchase #7	$118.70	11.148%	$131.9327	$131.93	$131.95	$131.90
7 purchase totals =	$964.90		$1,051.3972	$1,051.39	$1,051.45	$1,051.20