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	$129.40	9.178%	$141.2763	$141.28	$141.30	$141.30
Purchase #2	$156.94	9.286%	$171.5134	$171.51	$171.50	$171.50
Purchase #3	$156.59	10.347%	$172.7924	$172.79	$172.80	$172.80
Purchase #4	$128.41	4.663%	$134.3978	$134.40	$134.40	$134.40
Purchase #5	$58.61	8.292%	$63.4699	$63.47	$63.45	$63.50
Purchase #6	$232.67	4.680%	$243.559	$243.56	$243.55	$243.60
Purchase #7	$209.89	10.335%	$231.5821	$231.58	$231.60	$231.60
7 purchase totals =	$1,072.51		$1,158.5909	$1,158.59	$1,158.60	$1,158.70