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	$148.89	8.658%	$161.7809	$161.78	$161.80	$161.80
Purchase #2	$34.84	8.678%	$37.8634	$37.86	$37.85	$37.90
Purchase #3	$188.53	6.300%	$200.4074	$200.41	$200.40	$200.40
Purchase #4	$94.74	4.805%	$99.2923	$99.29	$99.30	$99.30
Purchase #5	$147.84	5.285%	$155.6533	$155.65	$155.65	$155.70
Purchase #6	$78.37	9.548%	$85.8528	$85.85	$85.85	$85.90
Purchase #7	$249.99	5.871%	$264.6669	$264.67	$264.65	$264.70
7 purchase totals =	$943.20		$1,005.5170	$1,005.51	$1,005.50	$1,005.70