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	$167.91	3.756%	$174.2167	$174.22	$174.20	$174.20
Purchase #2	$133.54	10.106%	$147.0356	$147.04	$147.05	$147.00
Purchase #3	$69.94	4.506%	$73.0915	$73.09	$73.10	$73.10
Purchase #4	$203.89	11.755%	$227.8573	$227.86	$227.85	$227.90
Purchase #5	$86.34	4.781%	$90.4679	$90.47	$90.45	$90.50
Purchase #6	$205.36	6.733%	$219.1869	$219.19	$219.20	$219.20
Purchase #7	$146.30	11.312%	$162.8495	$162.85	$162.85	$162.80
7 purchase totals =	$1,013.28		$1,094.7054	$1,094.72	$1,094.70	$1,094.70