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	$210.91	11.460%	$235.0803	$235.08	$235.10	$235.10
Purchase #2	$245.90	7.412%	$264.1261	$264.13	$264.15	$264.10
Purchase #3	$50.81	10.139%	$55.9616	$55.96	$55.95	$56.00
Purchase #4	$22.62	12.794%	$25.514	$25.51	$25.50	$25.50
Purchase #5	$37.72	6.434%	$40.1469	$40.15	$40.15	$40.10
Purchase #6	$174.83	9.268%	$191.0332	$191.03	$191.05	$191.00
Purchase #7	$181.27	8.118%	$195.9855	$195.99	$196.00	$196.00
7 purchase totals =	$924.06		$1,007.8476	$1,007.85	$1,007.90	$1,007.80