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	$200.50	9.270%	$219.0864	$219.09	$219.10	$219.10
Purchase #2	$92.86	12.282%	$104.2651	$104.27	$104.25	$104.30
Purchase #3	$31.71	7.452%	$34.073	$34.07	$34.05	$34.10
Purchase #4	$32.79	13.135%	$37.097	$37.10	$37.10	$37.10
Purchase #5	$19.54	7.786%	$21.0614	$21.06	$21.05	$21.10
Purchase #6	$82.55	9.204%	$90.1479	$90.15	$90.15	$90.10
Purchase #7	$96.64	3.620%	$100.1384	$100.14	$100.15	$100.10
7 purchase totals =	$556.59		$605.8692	$605.88	$605.85	$605.90