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	$167.61	10.855%	$185.8041	$185.80	$185.80	$185.80
Purchase #2	$31.95	5.239%	$33.6239	$33.62	$33.60	$33.60
Purchase #3	$24.29	5.265%	$25.5689	$25.57	$25.55	$25.60
Purchase #4	$190.53	12.842%	$214.9979	$215.00	$215.00	$215.00
Purchase #5	$128.95	13.284%	$146.0797	$146.08	$146.10	$146.10
Purchase #6	$161.89	4.223%	$168.7266	$168.73	$168.75	$168.70
Purchase #7	$145.93	11.198%	$162.2712	$162.27	$162.25	$162.30
7 purchase totals =	$851.15		$937.0723	$937.07	$937.05	$937.10