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	$60.63	10.351%	$66.9058	$66.91	$66.90	$66.90
Purchase #2	$177.55	4.708%	$185.9091	$185.91	$185.90	$185.90
Purchase #3	$154.81	4.112%	$161.1758	$161.18	$161.20	$161.20
Purchase #4	$242.90	11.723%	$271.3752	$271.38	$271.40	$271.40
Purchase #5	$225.54	11.695%	$251.9169	$251.92	$251.90	$251.90
Purchase #6	$41.86	5.871%	$44.3176	$44.32	$44.30	$44.30
Purchase #7	$77.75	6.482%	$82.7898	$82.79	$82.80	$82.80
7 purchase totals =	$981.04		$1,064.3902	$1,064.41	$1,064.40	$1,064.40