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	$72.92	7.224%	$78.1877	$78.19	$78.20	$78.20
Purchase #2	$241.47	11.532%	$269.3163	$269.32	$269.30	$269.30
Purchase #3	$233.94	4.112%	$243.5596	$243.56	$243.55	$243.60
Purchase #4	$41.92	13.597%	$47.6199	$47.62	$47.60	$47.60
Purchase #5	$129.43	3.851%	$134.4143	$134.41	$134.40	$134.40
Purchase #6	$142.89	6.731%	$152.5079	$152.51	$152.50	$152.50
Purchase #7	$135.31	13.164%	$153.1222	$153.12	$153.10	$153.10
7 purchase totals =	$997.88		$1,078.7279	$1,078.73	$1,078.65	$1,078.70