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	$174.79	7.499%	$187.8975	$187.90	$187.90	$187.90
Purchase #2	$159.55	8.316%	$172.8182	$172.82	$172.80	$172.80
Purchase #3	$196.87	3.785%	$204.3215	$204.32	$204.30	$204.30
Purchase #4	$180.85	8.487%	$196.1987	$196.20	$196.20	$196.20
Purchase #5	$43.34	9.350%	$47.3923	$47.39	$47.40	$47.40
Purchase #6	$137.64	7.798%	$148.3732	$148.37	$148.35	$148.40
Purchase #7	$102.28	8.508%	$110.982	$110.98	$111.00	$111.00
7 purchase totals =	$995.32		$1,067.9834	$1,067.98	$1,067.95	$1,068.00