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	$15.88	3.641%	$16.4582	$16.46	$16.45	$16.50
Purchase #2	$206.30	10.358%	$227.6686	$227.67	$227.65	$227.70
Purchase #3	$209.82	9.139%	$228.9954	$229.00	$229.00	$229.00
Purchase #4	$165.55	9.819%	$181.8054	$181.81	$181.80	$181.80
Purchase #5	$118.76	10.145%	$130.8082	$130.81	$130.80	$130.80
Purchase #6	$133.27	13.557%	$151.3374	$151.34	$151.35	$151.30
Purchase #7	$72.83	12.744%	$82.1115	$82.11	$82.10	$82.10
7 purchase totals =	$922.41		$1,019.1847	$1,019.20	$1,019.15	$1,019.20