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	$157.59	13.840%	$179.4005	$179.40	$179.40	$179.40
Purchase #2	$204.96	10.514%	$226.5095	$226.51	$226.50	$226.50
Purchase #3	$54.57	4.300%	$56.9165	$56.92	$56.90	$56.90
Purchase #4	$79.63	8.206%	$86.1644	$86.16	$86.15	$86.20
Purchase #5	$168.47	12.392%	$189.3468	$189.35	$189.35	$189.30
Purchase #6	$82.46	13.766%	$93.8114	$93.81	$93.80	$93.80
Purchase #7	$67.63	6.554%	$72.0625	$72.06	$72.05	$72.10
7 purchase totals =	$815.31		$904.2116	$904.21	$904.15	$904.20