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	$215.57	4.634%	$225.5595	$225.56	$225.55	$225.60
Purchase #2	$138.57	6.622%	$147.7461	$147.75	$147.75	$147.70
Purchase #3	$156.27	6.143%	$165.8697	$165.87	$165.85	$165.90
Purchase #4	$182.97	8.494%	$198.5115	$198.51	$198.50	$198.50
Purchase #5	$174.36	5.423%	$183.8155	$183.82	$183.80	$183.80
Purchase #6	$78.49	13.796%	$89.3185	$89.32	$89.30	$89.30
Purchase #7	$63.95	10.865%	$70.8982	$70.90	$70.90	$70.90
7 purchase totals =	$1,010.18		$1,081.7190	$1,081.73	$1,081.65	$1,081.70