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	$241.55	9.573%	$264.6736	$264.67	$264.65	$264.70
Purchase #2	$137.32	9.142%	$149.8738	$149.87	$149.85	$149.90
Purchase #3	$182.96	6.457%	$194.7737	$194.77	$194.75	$194.80
Purchase #4	$32.82	7.457%	$35.2674	$35.27	$35.25	$35.30
Purchase #5	$37.28	6.298%	$39.6279	$39.63	$39.65	$39.60
Purchase #6	$244.77	4.704%	$256.284	$256.28	$256.30	$256.30
Purchase #7	$128.46	12.712%	$144.7898	$144.79	$144.80	$144.80
7 purchase totals =	$1,005.16		$1,085.2902	$1,085.28	$1,085.25	$1,085.40