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	$184.52	6.346%	$196.2296	$196.23	$196.25	$196.20
Purchase #2	$29.71	11.692%	$33.1837	$33.18	$33.20	$33.20
Purchase #3	$73.77	8.684%	$80.1762	$80.18	$80.20	$80.20
Purchase #4	$189.86	3.550%	$196.6	$196.60	$196.60	$196.60
Purchase #5	$140.32	3.350%	$145.0207	$145.02	$145.00	$145.00
Purchase #6	$146.54	13.385%	$166.1544	$166.15	$166.15	$166.20
Purchase #7	$186.73	9.376%	$204.2378	$204.24	$204.25	$204.20
7 purchase totals =	$951.45		$1,021.6024	$1,021.60	$1,021.65	$1,021.60