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	$164.73	11.834%	$184.2241	$184.22	$184.20	$184.20
Purchase #2	$135.65	5.333%	$142.8842	$142.88	$142.90	$142.90
Purchase #3	$160.87	7.769%	$173.368	$173.37	$173.35	$173.40
Purchase #4	$239.70	4.471%	$250.417	$250.42	$250.40	$250.40
Purchase #5	$38.76	10.522%	$42.8383	$42.84	$42.85	$42.80
Purchase #6	$49.76	7.375%	$53.4298	$53.43	$53.45	$53.40
Purchase #7	$162.38	3.754%	$168.4757	$168.48	$168.50	$168.50
7 purchase totals =	$951.85		$1,015.6371	$1,015.64	$1,015.65	$1,015.60