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	$89.70	13.648%	$101.9423	$101.94	$101.95	$101.90
Purchase #2	$196.53	12.637%	$221.3655	$221.37	$221.35	$221.40
Purchase #3	$17.67	6.703%	$18.8544	$18.85	$18.85	$18.90
Purchase #4	$20.53	11.572%	$22.9057	$22.91	$22.90	$22.90
Purchase #5	$250.62	11.872%	$280.3736	$280.37	$280.35	$280.40
Purchase #6	$147.72	11.394%	$164.5512	$164.55	$164.55	$164.60
Purchase #7	$180.57	8.429%	$195.7902	$195.79	$195.80	$195.80
7 purchase totals =	$903.34		$1,005.7829	$1,005.78	$1,005.75	$1,005.90