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	$204.55	3.295%	$211.2899	$211.29	$211.30	$211.30
Purchase #2	$250.86	4.590%	$262.3745	$262.37	$262.35	$262.40
Purchase #3	$116.65	12.194%	$130.8743	$130.87	$130.85	$130.90
Purchase #4	$20.88	4.407%	$21.8002	$21.80	$21.80	$21.80
Purchase #5	$248.95	3.227%	$256.9836	$256.98	$257.00	$257.00
Purchase #6	$114.28	11.476%	$127.3948	$127.39	$127.40	$127.40
Purchase #7	$73.30	10.200%	$80.7766	$80.78	$80.80	$80.80
7 purchase totals =	$1,029.47		$1,091.4939	$1,091.48	$1,091.50	$1,091.60