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	$191.70	9.288%	$209.5051	$209.51	$209.50	$209.50
Purchase #2	$72.37	10.482%	$79.9558	$79.96	$79.95	$80.00
Purchase #3	$245.44	11.277%	$273.1183	$273.12	$273.10	$273.10
Purchase #4	$77.69	7.185%	$83.272	$83.27	$83.25	$83.30
Purchase #5	$50.67	11.108%	$56.2984	$56.30	$56.30	$56.30
Purchase #6	$131.31	3.827%	$136.3352	$136.34	$136.35	$136.30
Purchase #7	$221.72	10.732%	$245.515	$245.52	$245.50	$245.50
7 purchase totals =	$990.90		$1,083.9998	$1,084.02	$1,083.95	$1,084.00