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	$197.76	6.118%	$209.859	$209.86	$209.85	$209.90
Purchase #2	$212.95	6.650%	$227.1112	$227.11	$227.10	$227.10
Purchase #3	$97.28	6.833%	$103.9271	$103.93	$103.95	$103.90
Purchase #4	$100.57	10.691%	$111.3219	$111.32	$111.30	$111.30
Purchase #5	$200.33	10.847%	$222.0598	$222.06	$222.05	$222.10
Purchase #6	$172.63	12.633%	$194.4383	$194.44	$194.45	$194.40
Purchase #7	$245.83	9.479%	$269.1322	$269.13	$269.15	$269.10
7 purchase totals =	$1,227.35		$1,337.8495	$1,337.85	$1,337.85	$1,337.80