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	$250.29	12.357%	$281.2183	$281.22	$281.20	$281.20
Purchase #2	$72.92	7.764%	$78.5815	$78.58	$78.60	$78.60
Purchase #3	$38.68	9.304%	$42.2788	$42.28	$42.30	$42.30
Purchase #4	$227.98	4.739%	$238.784	$238.78	$238.80	$238.80
Purchase #5	$142.71	11.855%	$159.6283	$159.63	$159.65	$159.60
Purchase #6	$158.27	8.513%	$171.7435	$171.74	$171.75	$171.70
Purchase #7	$195.73	4.107%	$203.7686	$203.77	$203.75	$203.80
7 purchase totals =	$1,086.58		$1,176.0030	$1,176.00	$1,176.05	$1,176.00