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	$125.66	6.280%	$133.5514	$133.55	$133.55	$133.60
Purchase #2	$162.70	3.833%	$168.9363	$168.94	$168.95	$168.90
Purchase #3	$211.53	5.162%	$222.4492	$222.45	$222.45	$222.40
Purchase #4	$147.52	10.244%	$162.6319	$162.63	$162.65	$162.60
Purchase #5	$22.75	7.648%	$24.4899	$24.49	$24.50	$24.50
Purchase #6	$197.40	10.448%	$218.0244	$218.02	$218.00	$218.00
Purchase #7	$82.40	3.179%	$85.0195	$85.02	$85.00	$85.00
7 purchase totals =	$949.96		$1,015.1026	$1,015.10	$1,015.10	$1,015.00