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	$173.39	8.175%	$187.5646	$187.56	$187.55	$187.60
Purchase #2	$229.80	6.294%	$244.2636	$244.26	$244.25	$244.30
Purchase #3	$81.43	13.590%	$92.4963	$92.50	$92.50	$92.50
Purchase #4	$111.27	4.697%	$116.4964	$116.50	$116.50	$116.50
Purchase #5	$48.85	7.120%	$52.3281	$52.33	$52.35	$52.30
Purchase #6	$84.37	8.452%	$91.501	$91.50	$91.50	$91.50
Purchase #7	$135.46	13.798%	$154.1508	$154.15	$154.15	$154.20
7 purchase totals =	$864.57		$938.8008	$938.80	$938.80	$938.90