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	$64.74	9.704%	$71.0224	$71.02	$71.00	$71.00
Purchase #2	$65.65	10.535%	$72.5662	$72.57	$72.55	$72.60
Purchase #3	$86.92	5.294%	$91.5215	$91.52	$91.50	$91.50
Purchase #4	$243.33	6.761%	$259.7815	$259.78	$259.80	$259.80
Purchase #5	$242.60	11.695%	$270.9721	$270.97	$270.95	$271.00
Purchase #6	$191.27	4.286%	$199.4678	$199.47	$199.45	$199.50
Purchase #7	$131.44	11.282%	$146.2691	$146.27	$146.25	$146.30
7 purchase totals =	$1,025.95		$1,111.6006	$1,111.60	$1,111.50	$1,111.70