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	$175.46	6.604%	$187.0474	$187.05	$187.05	$187.00
Purchase #2	$125.93	4.492%	$131.5868	$131.59	$131.60	$131.60
Purchase #3	$249.73	11.662%	$278.8535	$278.85	$278.85	$278.90
Purchase #4	$137.37	10.316%	$151.5411	$151.54	$151.55	$151.50
Purchase #5	$110.70	8.533%	$120.146	$120.15	$120.15	$120.10
Purchase #6	$144.98	8.475%	$157.2671	$157.27	$157.25	$157.30
Purchase #7	$147.69	13.485%	$167.606	$167.61	$167.60	$167.60
7 purchase totals =	$1,091.86		$1,194.0479	$1,194.06	$1,194.05	$1,194.00