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	$241.63	10.617%	$267.2839	$267.28	$267.30	$267.30
Purchase #2	$66.91	7.550%	$71.9617	$71.96	$71.95	$72.00
Purchase #3	$61.34	9.369%	$67.0869	$67.09	$67.10	$67.10
Purchase #4	$57.90	12.123%	$64.9192	$64.92	$64.90	$64.90
Purchase #5	$33.37	6.130%	$35.4156	$35.42	$35.40	$35.40
Purchase #6	$160.30	3.267%	$165.537	$165.54	$165.55	$165.50
Purchase #7	$156.77	9.272%	$171.3057	$171.31	$171.30	$171.30
7 purchase totals =	$778.22		$843.5100	$843.52	$843.50	$843.50