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	$173.75	8.238%	$188.0635	$188.06	$188.05	$188.10
Purchase #2	$219.56	10.356%	$242.2976	$242.30	$242.30	$242.30
Purchase #3	$233.33	9.445%	$255.368	$255.37	$255.35	$255.40
Purchase #4	$149.58	12.649%	$168.5004	$168.50	$168.50	$168.50
Purchase #5	$90.26	3.556%	$93.4696	$93.47	$93.45	$93.50
Purchase #6	$54.51	9.538%	$59.7092	$59.71	$59.70	$59.70
Purchase #7	$61.38	8.800%	$66.7814	$66.78	$66.80	$66.80
7 purchase totals =	$982.37		$1,074.1897	$1,074.19	$1,074.15	$1,074.30