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	$162.43	13.164%	$183.8123	$183.81	$183.80	$183.80
Purchase #2	$152.92	12.623%	$172.2231	$172.22	$172.20	$172.20
Purchase #3	$99.72	5.601%	$105.3053	$105.31	$105.30	$105.30
Purchase #4	$247.52	10.415%	$273.2992	$273.30	$273.30	$273.30
Purchase #5	$160.97	8.691%	$174.9599	$174.96	$174.95	$175.00
Purchase #6	$139.67	5.603%	$147.4957	$147.50	$147.50	$147.50
Purchase #7	$44.44	5.492%	$46.8806	$46.88	$46.90	$46.90
7 purchase totals =	$1,007.67		$1,103.9761	$1,103.98	$1,103.95	$1,104.00