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	$94.38	11.759%	$105.4781	$105.48	$105.50	$105.50
Purchase #2	$90.90	7.177%	$97.4239	$97.42	$97.40	$97.40
Purchase #3	$170.83	9.592%	$187.216	$187.22	$187.20	$187.20
Purchase #4	$209.96	8.487%	$227.7793	$227.78	$227.80	$227.80
Purchase #5	$233.39	3.353%	$241.2156	$241.22	$241.20	$241.20
Purchase #6	$141.48	7.218%	$151.692	$151.69	$151.70	$151.70
Purchase #7	$159.28	10.434%	$175.8993	$175.90	$175.90	$175.90
7 purchase totals =	$1,100.22		$1,186.7042	$1,186.71	$1,186.70	$1,186.70