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	$69.55	11.361%	$77.4516	$77.45	$77.45	$77.50
Purchase #2	$144.39	4.391%	$150.7302	$150.73	$150.75	$150.70
Purchase #3	$110.35	6.846%	$117.9046	$117.90	$117.90	$117.90
Purchase #4	$210.39	9.803%	$231.0145	$231.01	$231.00	$231.00
Purchase #5	$94.38	5.375%	$99.4529	$99.45	$99.45	$99.50
Purchase #6	$156.57	12.271%	$175.7827	$175.78	$175.80	$175.80
Purchase #7	$160.88	7.374%	$172.7433	$172.74	$172.75	$172.70
7 purchase totals =	$946.51		$1,025.0798	$1,025.06	$1,025.10	$1,025.10