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	$122.25	4.503%	$127.7549	$127.75	$127.75	$127.80
Purchase #2	$9.90	7.148%	$10.6077	$10.61	$10.60	$10.60
Purchase #3	$197.86	11.734%	$221.0769	$221.08	$221.10	$221.10
Purchase #4	$242.48	4.503%	$253.3989	$253.40	$253.40	$253.40
Purchase #5	$186.60	6.365%	$198.4771	$198.48	$198.50	$198.50
Purchase #6	$223.39	5.362%	$235.3682	$235.37	$235.35	$235.40
Purchase #7	$127.74	13.233%	$144.6438	$144.64	$144.65	$144.60
7 purchase totals =	$1,110.22		$1,191.3275	$1,191.33	$1,191.35	$1,191.40