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	$77.54	10.222%	$85.4661	$85.47	$85.45	$85.50
Purchase #2	$249.60	5.605%	$263.5901	$263.59	$263.60	$263.60
Purchase #3	$146.97	3.382%	$151.9405	$151.94	$151.95	$151.90
Purchase #4	$195.33	12.148%	$219.0587	$219.06	$219.05	$219.10
Purchase #5	$55.62	8.815%	$60.5229	$60.52	$60.50	$60.50
Purchase #6	$137.81	13.713%	$156.7079	$156.71	$156.70	$156.70
Purchase #7	$79.88	3.181%	$82.421	$82.42	$82.40	$82.40
7 purchase totals =	$942.75		$1,019.7072	$1,019.71	$1,019.65	$1,019.70