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	$106.33	11.150%	$118.1858	$118.19	$118.20	$118.20
Purchase #2	$84.91	5.130%	$89.2659	$89.27	$89.25	$89.30
Purchase #3	$175.82	7.722%	$189.3968	$189.40	$189.40	$189.40
Purchase #4	$247.47	11.480%	$275.8796	$275.88	$275.90	$275.90
Purchase #5	$85.63	3.291%	$88.4481	$88.45	$88.45	$88.40
Purchase #6	$160.44	5.148%	$168.6995	$168.70	$168.70	$168.70
Purchase #7	$96.48	7.774%	$103.9804	$103.98	$104.00	$104.00
7 purchase totals =	$957.08		$1,033.8561	$1,033.87	$1,033.90	$1,033.90