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	$179.35	6.790%	$191.5279	$191.53	$191.55	$191.50
Purchase #2	$99.95	9.487%	$109.4323	$109.43	$109.45	$109.40
Purchase #3	$51.69	10.482%	$57.1081	$57.11	$57.10	$57.10
Purchase #4	$113.36	12.628%	$127.6751	$127.68	$127.70	$127.70
Purchase #5	$22.89	6.144%	$24.2964	$24.30	$24.30	$24.30
Purchase #6	$246.64	7.594%	$265.3698	$265.37	$265.35	$265.40
Purchase #7	$45.65	9.305%	$49.8977	$49.90	$49.90	$49.90
7 purchase totals =	$759.53		$825.3073	$825.32	$825.35	$825.30