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	$87.29	10.572%	$96.5183	$96.52	$96.50	$96.50
Purchase #2	$196.62	12.263%	$220.7315	$220.73	$220.75	$220.70
Purchase #3	$222.88	11.478%	$248.4622	$248.46	$248.45	$248.50
Purchase #4	$37.74	13.732%	$42.9225	$42.92	$42.90	$42.90
Purchase #5	$180.72	5.774%	$191.1548	$191.15	$191.15	$191.20
Purchase #6	$94.90	8.639%	$103.0984	$103.10	$103.10	$103.10
Purchase #7	$196.37	4.398%	$205.0064	$205.01	$205.00	$205.00
7 purchase totals =	$1,016.52		$1,107.8941	$1,107.89	$1,107.85	$1,107.90