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	$212.38	9.353%	$232.2439	$232.24	$232.25	$232.20
Purchase #2	$195.59	7.573%	$210.402	$210.40	$210.40	$210.40
Purchase #3	$109.27	12.308%	$122.719	$122.72	$122.70	$122.70
Purchase #4	$130.78	11.704%	$146.0865	$146.09	$146.10	$146.10
Purchase #5	$85.56	8.555%	$92.8797	$92.88	$92.90	$92.90
Purchase #6	$145.74	7.380%	$156.4956	$156.50	$156.50	$156.50
Purchase #7	$104.86	6.297%	$111.463	$111.46	$111.45	$111.50
7 purchase totals =	$984.18		$1,072.2897	$1,072.29	$1,072.30	$1,072.30