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	$47.85	9.490%	$52.391	$52.39	$52.40	$52.40
Purchase #2	$73.44	11.563%	$81.9319	$81.93	$81.95	$81.90
Purchase #3	$212.96	13.702%	$242.1398	$242.14	$242.15	$242.10
Purchase #4	$91.39	12.847%	$103.1309	$103.13	$103.15	$103.10
Purchase #5	$70.54	11.389%	$78.5738	$78.57	$78.55	$78.60
Purchase #6	$66.35	6.536%	$70.6866	$70.69	$70.70	$70.70
Purchase #7	$98.96	4.142%	$103.0589	$103.06	$103.05	$103.10
7 purchase totals =	$661.49		$731.9129	$731.91	$731.95	$731.90