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	$238.33	5.205%	$250.7351	$250.74	$250.75	$250.70
Purchase #2	$165.39	12.523%	$186.1018	$186.10	$186.10	$186.10
Purchase #3	$57.66	10.754%	$63.8608	$63.86	$63.85	$63.90
Purchase #4	$181.39	13.536%	$205.943	$205.94	$205.95	$205.90
Purchase #5	$155.54	4.705%	$162.8582	$162.86	$162.85	$162.90
Purchase #6	$179.89	7.512%	$193.4033	$193.40	$193.40	$193.40
Purchase #7	$101.87	7.414%	$109.4226	$109.42	$109.40	$109.40
7 purchase totals =	$1,080.07		$1,172.3248	$1,172.32	$1,172.30	$1,172.30