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	$54.78	8.675%	$59.5322	$59.53	$59.55	$59.50
Purchase #2	$184.57	5.366%	$194.474	$194.47	$194.45	$194.50
Purchase #3	$42.90	11.405%	$47.7927	$47.79	$47.80	$47.80
Purchase #4	$124.94	12.782%	$140.9098	$140.91	$140.90	$140.90
Purchase #5	$47.88	12.690%	$53.956	$53.96	$53.95	$54.00
Purchase #6	$46.74	13.500%	$53.0499	$53.05	$53.05	$53.00
Purchase #7	$128.83	9.472%	$141.0328	$141.03	$141.05	$141.00
7 purchase totals =	$630.64		$690.7474	$690.74	$690.75	$690.70