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	$127.59	4.538%	$133.38	$133.38	$133.40	$133.40
Purchase #2	$186.56	12.192%	$209.3054	$209.31	$209.30	$209.30
Purchase #3	$220.87	6.606%	$235.4607	$235.46	$235.45	$235.50
Purchase #4	$38.69	3.242%	$39.9443	$39.94	$39.95	$39.90
Purchase #5	$33.97	11.340%	$37.8222	$37.82	$37.80	$37.80
Purchase #6	$183.63	7.165%	$196.7871	$196.79	$196.80	$196.80
Purchase #7	$125.28	13.375%	$142.0362	$142.04	$142.05	$142.00
7 purchase totals =	$916.59		$994.7359	$994.74	$994.75	$994.70