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	$174.48	6.227%	$185.3449	$185.34	$185.35	$185.30
Purchase #2	$189.66	12.709%	$213.7639	$213.76	$213.75	$213.80
Purchase #3	$162.78	13.670%	$185.032	$185.03	$185.05	$185.00
Purchase #4	$181.47	4.361%	$189.3839	$189.38	$189.40	$189.40
Purchase #5	$104.34	8.799%	$113.5209	$113.52	$113.50	$113.50
Purchase #6	$143.36	10.667%	$158.6522	$158.65	$158.65	$158.70
Purchase #7	$249.35	5.143%	$262.1741	$262.17	$262.15	$262.20
7 purchase totals =	$1,205.44		$1,307.8719	$1,307.85	$1,307.85	$1,307.90