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	$98.61	5.385%	$103.9201	$103.92	$103.90	$103.90
Purchase #2	$37.41	13.243%	$42.3642	$42.36	$42.35	$42.40
Purchase #3	$82.74	8.856%	$90.0675	$90.07	$90.05	$90.10
Purchase #4	$194.69	12.104%	$218.2553	$218.26	$218.25	$218.30
Purchase #5	$229.71	5.171%	$241.5883	$241.59	$241.60	$241.60
Purchase #6	$71.95	3.680%	$74.5978	$74.60	$74.60	$74.60
Purchase #7	$188.75	3.566%	$195.4808	$195.48	$195.50	$195.50
7 purchase totals =	$903.86		$966.2740	$966.28	$966.25	$966.40