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	$187.79	4.551%	$196.3363	$196.34	$196.35	$196.30
Purchase #2	$163.74	13.505%	$185.8531	$185.85	$185.85	$185.90
Purchase #3	$229.56	4.294%	$239.4173	$239.42	$239.40	$239.40
Purchase #4	$118.58	5.179%	$124.7213	$124.72	$124.70	$124.70
Purchase #5	$167.69	7.146%	$179.6731	$179.67	$179.65	$179.70
Purchase #6	$124.31	12.361%	$139.676	$139.68	$139.70	$139.70
Purchase #7	$167.66	10.735%	$185.6583	$185.66	$185.65	$185.70
7 purchase totals =	$1,159.33		$1,251.3354	$1,251.34	$1,251.30	$1,251.40