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	$175.52	9.299%	$191.8416	$191.84	$191.85	$191.80
Purchase #2	$63.55	5.571%	$67.0904	$67.09	$67.10	$67.10
Purchase #3	$148.63	12.163%	$166.7079	$166.71	$166.70	$166.70
Purchase #4	$149.57	12.173%	$167.7772	$167.78	$167.80	$167.80
Purchase #5	$216.33	5.690%	$228.6392	$228.64	$228.65	$228.60
Purchase #6	$77.73	7.114%	$83.2597	$83.26	$83.25	$83.30
Purchase #7	$156.71	5.752%	$165.724	$165.72	$165.70	$165.70
7 purchase totals =	$988.04		$1,071.0400	$1,071.04	$1,071.05	$1,071.00