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	$74.69	4.526%	$78.0705	$78.07	$78.05	$78.10
Purchase #2	$224.54	6.505%	$239.1463	$239.15	$239.15	$239.10
Purchase #3	$122.85	4.228%	$128.0441	$128.04	$128.05	$128.00
Purchase #4	$200.42	5.824%	$212.0925	$212.09	$212.10	$212.10
Purchase #5	$94.72	10.867%	$105.0132	$105.01	$105.00	$105.00
Purchase #6	$130.61	10.263%	$144.0145	$144.01	$144.00	$144.00
Purchase #7	$139.43	4.439%	$145.6193	$145.62	$145.60	$145.60
7 purchase totals =	$987.26		$1,052.0004	$1,051.99	$1,051.95	$1,051.90