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	$221.42	10.530%	$244.7355	$244.74	$244.75	$244.70
Purchase #2	$207.44	9.133%	$226.3855	$226.39	$226.40	$226.40
Purchase #3	$91.76	13.624%	$104.2614	$104.26	$104.25	$104.30
Purchase #4	$78.94	4.473%	$82.471	$82.47	$82.45	$82.50
Purchase #5	$91.69	12.378%	$103.0394	$103.04	$103.05	$103.00
Purchase #6	$178.59	6.787%	$190.7109	$190.71	$190.70	$190.70
Purchase #7	$185.27	13.629%	$210.5204	$210.52	$210.50	$210.50
7 purchase totals =	$1,055.11		$1,162.1241	$1,162.13	$1,162.10	$1,162.10