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	$155.49	4.417%	$162.358	$162.36	$162.35	$162.40
Purchase #2	$240.41	10.164%	$264.8453	$264.85	$264.85	$264.80
Purchase #3	$91.88	10.634%	$101.6505	$101.65	$101.65	$101.70
Purchase #4	$94.39	11.825%	$105.5516	$105.55	$105.55	$105.60
Purchase #5	$48.65	12.520%	$54.741	$54.74	$54.75	$54.70
Purchase #6	$200.37	9.816%	$220.0383	$220.04	$220.05	$220.00
Purchase #7	$98.81	13.680%	$112.3272	$112.33	$112.35	$112.30
7 purchase totals =	$930.00		$1,021.5119	$1,021.52	$1,021.55	$1,021.50