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	$187.31	6.705%	$199.8691	$199.87	$199.85	$199.90
Purchase #2	$31.28	3.612%	$32.4098	$32.41	$32.40	$32.40
Purchase #3	$85.27	9.394%	$93.2803	$93.28	$93.30	$93.30
Purchase #4	$82.32	13.677%	$93.5789	$93.58	$93.60	$93.60
Purchase #5	$225.66	11.330%	$251.2273	$251.23	$251.25	$251.20
Purchase #6	$110.42	7.366%	$118.5535	$118.55	$118.55	$118.60
Purchase #7	$80.39	12.753%	$90.6421	$90.64	$90.65	$90.60
7 purchase totals =	$802.65		$879.5610	$879.56	$879.60	$879.60