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	$33.48	7.573%	$36.0154	$36.02	$36.00	$36.00
Purchase #2	$188.38	4.496%	$196.8496	$196.85	$196.85	$196.80
Purchase #3	$130.65	11.665%	$145.8903	$145.89	$145.90	$145.90
Purchase #4	$242.87	6.206%	$257.9425	$257.94	$257.95	$257.90
Purchase #5	$147.72	10.293%	$162.9248	$162.92	$162.90	$162.90
Purchase #6	$139.77	6.630%	$149.0368	$149.04	$149.05	$149.00
Purchase #7	$209.97	4.108%	$218.5956	$218.60	$218.60	$218.60
7 purchase totals =	$1,092.84		$1,167.2550	$1,167.26	$1,167.25	$1,167.10