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	$151.36	9.516%	$165.7634	$165.76	$165.75	$165.80
Purchase #2	$104.85	5.448%	$110.5622	$110.56	$110.55	$110.60
Purchase #3	$137.32	5.804%	$145.2901	$145.29	$145.30	$145.30
Purchase #4	$135.61	10.122%	$149.3364	$149.34	$149.35	$149.30
Purchase #5	$57.61	9.133%	$62.8715	$62.87	$62.85	$62.90
Purchase #6	$94.33	6.174%	$100.1539	$100.15	$100.15	$100.20
Purchase #7	$178.25	5.799%	$188.5867	$188.59	$188.60	$188.60
7 purchase totals =	$859.33		$922.5642	$922.56	$922.55	$922.70