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	$214.35	9.787%	$235.3284	$235.33	$235.35	$235.30
Purchase #2	$71.52	9.426%	$78.2615	$78.26	$78.25	$78.30
Purchase #3	$95.63	10.616%	$105.7821	$105.78	$105.80	$105.80
Purchase #4	$41.94	5.664%	$44.3155	$44.32	$44.30	$44.30
Purchase #5	$171.86	5.298%	$180.9651	$180.97	$180.95	$181.00
Purchase #6	$86.48	10.506%	$95.5656	$95.57	$95.55	$95.60
Purchase #7	$56.92	12.851%	$64.2348	$64.23	$64.25	$64.20
7 purchase totals =	$738.70		$804.4530	$804.46	$804.45	$804.50