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	$103.47	6.573%	$110.2711	$110.27	$110.25	$110.30
Purchase #2	$152.64	12.711%	$172.0421	$172.04	$172.05	$172.00
Purchase #3	$169.66	12.359%	$190.6283	$190.63	$190.65	$190.60
Purchase #4	$121.96	6.503%	$129.8911	$129.89	$129.90	$129.90
Purchase #5	$158.74	5.517%	$167.4977	$167.50	$167.50	$167.50
Purchase #6	$41.71	13.457%	$47.3229	$47.32	$47.30	$47.30
Purchase #7	$116.43	9.627%	$127.6387	$127.64	$127.65	$127.60
7 purchase totals =	$864.61		$945.2919	$945.29	$945.30	$945.20