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	$164.65	6.355%	$175.1135	$175.11	$175.10	$175.10
Purchase #2	$98.56	5.127%	$103.6132	$103.61	$103.60	$103.60
Purchase #3	$215.48	10.854%	$238.8682	$238.87	$238.85	$238.90
Purchase #4	$79.70	4.427%	$83.2283	$83.23	$83.25	$83.20
Purchase #5	$68.71	4.224%	$71.6123	$71.61	$71.60	$71.60
Purchase #6	$72.31	13.224%	$81.8723	$81.87	$81.85	$81.90
Purchase #7	$163.37	4.548%	$170.8001	$170.80	$170.80	$170.80
7 purchase totals =	$862.78		$925.1079	$925.10	$925.05	$925.10