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	$198.26	9.589%	$217.2712	$217.27	$217.25	$217.30
Purchase #2	$110.56	7.739%	$119.1162	$119.12	$119.10	$119.10
Purchase #3	$216.58	7.104%	$231.9658	$231.97	$231.95	$232.00
Purchase #4	$37.89	11.848%	$42.3792	$42.38	$42.40	$42.40
Purchase #5	$78.98	8.424%	$85.6333	$85.63	$85.65	$85.60
Purchase #6	$66.73	7.680%	$71.8549	$71.85	$71.85	$71.90
Purchase #7	$216.58	12.338%	$243.3016	$243.30	$243.30	$243.30
7 purchase totals =	$925.58		$1,011.5222	$1,011.52	$1,011.50	$1,011.60