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	$78.97	13.256%	$89.4383	$89.44	$89.45	$89.40
Purchase #2	$52.66	13.568%	$59.8049	$59.80	$59.80	$59.80
Purchase #3	$175.35	12.226%	$196.7883	$196.79	$196.80	$196.80
Purchase #4	$214.76	12.676%	$241.983	$241.98	$242.00	$242.00
Purchase #5	$55.76	4.721%	$58.3924	$58.39	$58.40	$58.40
Purchase #6	$209.87	11.163%	$233.2978	$233.30	$233.30	$233.30
Purchase #7	$37.84	12.329%	$42.5053	$42.51	$42.50	$42.50
7 purchase totals =	$825.21		$922.2100	$922.21	$922.25	$922.20