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	$49.40	7.171%	$52.9425	$52.94	$52.95	$52.90
Purchase #2	$214.86	13.486%	$243.836	$243.84	$243.85	$243.80
Purchase #3	$215.77	3.136%	$222.5365	$222.54	$222.55	$222.50
Purchase #4	$159.95	4.216%	$166.6935	$166.69	$166.70	$166.70
Purchase #5	$73.56	10.821%	$81.5199	$81.52	$81.50	$81.50
Purchase #6	$228.45	6.859%	$244.1194	$244.12	$244.10	$244.10
Purchase #7	$73.44	6.667%	$78.3362	$78.34	$78.35	$78.30
7 purchase totals =	$1,015.43		$1,089.9840	$1,089.99	$1,090.00	$1,089.80