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	$89.63	10.336%	$98.8942	$98.89	$98.90	$98.90
Purchase #2	$186.33	10.199%	$205.3338	$205.33	$205.35	$205.30
Purchase #3	$51.31	8.610%	$55.7278	$55.73	$55.75	$55.70
Purchase #4	$230.97	6.233%	$245.3664	$245.37	$245.35	$245.40
Purchase #5	$131.27	6.281%	$139.5151	$139.52	$139.50	$139.50
Purchase #6	$228.92	5.487%	$241.4808	$241.48	$241.50	$241.50
Purchase #7	$100.52	8.768%	$109.3336	$109.33	$109.35	$109.30
7 purchase totals =	$1,018.95		$1,095.6517	$1,095.65	$1,095.70	$1,095.60