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	$153.85	7.615%	$165.5657	$165.57	$165.55	$165.60
Purchase #2	$227.90	6.384%	$242.4491	$242.45	$242.45	$242.40
Purchase #3	$223.80	13.615%	$254.2704	$254.27	$254.25	$254.30
Purchase #4	$97.97	10.676%	$108.4293	$108.43	$108.45	$108.40
Purchase #5	$177.56	10.587%	$196.3583	$196.36	$196.35	$196.40
Purchase #6	$93.86	6.343%	$99.8135	$99.81	$99.80	$99.80
Purchase #7	$211.75	12.755%	$238.7587	$238.76	$238.75	$238.80
7 purchase totals =	$1,186.69		$1,305.6450	$1,305.65	$1,305.60	$1,305.70