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	$92.96	7.766%	$100.1793	$100.18	$100.20	$100.20
Purchase #2	$243.67	9.163%	$265.9975	$266.00	$266.00	$266.00
Purchase #3	$59.58	6.667%	$63.5522	$63.55	$63.55	$63.60
Purchase #4	$137.88	12.180%	$154.6738	$154.67	$154.65	$154.70
Purchase #5	$67.29	6.801%	$71.8664	$71.87	$71.85	$71.90
Purchase #6	$147.38	13.483%	$167.2512	$167.25	$167.25	$167.30
Purchase #7	$115.90	7.696%	$124.8197	$124.82	$124.80	$124.80
7 purchase totals =	$864.66		$948.3401	$948.34	$948.30	$948.50