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	$208.58	6.328%	$221.7789	$221.78	$221.80	$221.80
Purchase #2	$64.69	13.431%	$73.3785	$73.38	$73.40	$73.40
Purchase #3	$153.47	10.317%	$169.3035	$169.30	$169.30	$169.30
Purchase #4	$160.85	5.179%	$169.1804	$169.18	$169.20	$169.20
Purchase #5	$117.44	8.376%	$127.2768	$127.28	$127.30	$127.30
Purchase #6	$48.36	11.681%	$54.0089	$54.01	$54.00	$54.00
Purchase #7	$218.89	12.104%	$245.3844	$245.38	$245.40	$245.40
7 purchase totals =	$972.28		$1,060.3114	$1,060.31	$1,060.40	$1,060.40