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	$201.51	6.786%	$215.1845	$215.18	$215.20	$215.20
Purchase #2	$169.60	4.760%	$177.673	$177.67	$177.65	$177.70
Purchase #3	$40.86	12.846%	$46.1089	$46.11	$46.10	$46.10
Purchase #4	$98.94	4.535%	$103.4269	$103.43	$103.45	$103.40
Purchase #5	$62.74	13.516%	$71.2199	$71.22	$71.20	$71.20
Purchase #6	$161.52	4.148%	$168.2198	$168.22	$168.20	$168.20
Purchase #7	$215.96	5.258%	$227.3152	$227.32	$227.30	$227.30
7 purchase totals =	$951.13		$1,009.1482	$1,009.15	$1,009.10	$1,009.10