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	$220.42	3.872%	$228.9547	$228.95	$228.95	$229.00
Purchase #2	$78.53	5.252%	$82.6544	$82.65	$82.65	$82.70
Purchase #3	$79.25	7.594%	$85.2682	$85.27	$85.25	$85.30
Purchase #4	$134.91	5.472%	$142.2923	$142.29	$142.30	$142.30
Purchase #5	$104.46	12.466%	$117.482	$117.48	$117.50	$117.50
Purchase #6	$197.63	6.491%	$210.4582	$210.46	$210.45	$210.50
Purchase #7	$191.83	9.610%	$210.2649	$210.26	$210.25	$210.30
7 purchase totals =	$1,007.03		$1,077.3747	$1,077.36	$1,077.35	$1,077.60