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	$186.96	10.238%	$206.101	$206.10	$206.10	$206.10
Purchase #2	$37.48	11.451%	$41.7718	$41.77	$41.75	$41.80
Purchase #3	$91.74	12.793%	$103.4763	$103.48	$103.50	$103.50
Purchase #4	$87.83	3.113%	$90.5641	$90.56	$90.55	$90.60
Purchase #5	$210.76	12.644%	$237.4085	$237.41	$237.40	$237.40
Purchase #6	$128.99	4.370%	$134.6269	$134.63	$134.65	$134.60
Purchase #7	$237.81	4.477%	$248.4568	$248.46	$248.45	$248.50
7 purchase totals =	$981.57		$1,062.4054	$1,062.41	$1,062.40	$1,062.50