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	$122.49	6.803%	$130.823	$130.82	$130.80	$130.80
Purchase #2	$177.81	7.444%	$191.0462	$191.05	$191.05	$191.00
Purchase #3	$181.27	13.824%	$206.3288	$206.33	$206.35	$206.30
Purchase #4	$71.38	9.793%	$78.3702	$78.37	$78.35	$78.40
Purchase #5	$27.31	8.236%	$29.5593	$29.56	$29.55	$29.60
Purchase #6	$185.54	7.535%	$199.5204	$199.52	$199.50	$199.50
Purchase #7	$159.91	13.698%	$181.8145	$181.81	$181.80	$181.80
7 purchase totals =	$925.71		$1,017.4624	$1,017.46	$1,017.40	$1,017.40