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	$95.94	3.843%	$99.627	$99.63	$99.65	$99.60
Purchase #2	$168.87	13.652%	$191.9241	$191.92	$191.90	$191.90
Purchase #3	$142.56	7.257%	$152.9056	$152.91	$152.90	$152.90
Purchase #4	$118.69	13.780%	$135.0455	$135.05	$135.05	$135.00
Purchase #5	$236.70	10.711%	$262.0529	$262.05	$262.05	$262.10
Purchase #6	$149.66	11.261%	$166.5132	$166.51	$166.50	$166.50
Purchase #7	$128.30	8.546%	$139.2645	$139.26	$139.25	$139.30
7 purchase totals =	$1,040.72		$1,147.3328	$1,147.33	$1,147.30	$1,147.30