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	$211.52	9.551%	$231.7223	$231.72	$231.70	$231.70
Purchase #2	$99.45	11.584%	$110.9703	$110.97	$110.95	$111.00
Purchase #3	$27.74	12.473%	$31.2	$31.20	$31.20	$31.20
Purchase #4	$155.92	9.791%	$171.1861	$171.19	$171.20	$171.20
Purchase #5	$57.49	3.297%	$59.3854	$59.39	$59.40	$59.40
Purchase #6	$60.27	12.486%	$67.7953	$67.80	$67.80	$67.80
Purchase #7	$200.53	5.380%	$211.3185	$211.32	$211.30	$211.30
7 purchase totals =	$812.92		$883.5779	$883.59	$883.55	$883.60