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	$178.97	7.787%	$192.9064	$192.91	$192.90	$192.90
Purchase #2	$79.57	12.820%	$89.7709	$89.77	$89.75	$89.80
Purchase #3	$189.86	5.560%	$200.4162	$200.42	$200.40	$200.40
Purchase #4	$49.54	13.619%	$56.2869	$56.29	$56.30	$56.30
Purchase #5	$171.80	12.551%	$193.3626	$193.36	$193.35	$193.40
Purchase #6	$72.70	5.264%	$76.5269	$76.53	$76.55	$76.50
Purchase #7	$236.29	8.718%	$256.8898	$256.89	$256.90	$256.90
7 purchase totals =	$978.73		$1,066.1597	$1,066.17	$1,066.15	$1,066.20