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	$155.26	9.228%	$169.5874	$169.59	$169.60	$169.60
Purchase #2	$162.76	10.666%	$180.12	$180.12	$180.10	$180.10
Purchase #3	$185.28	8.137%	$200.3562	$200.36	$200.35	$200.40
Purchase #4	$185.72	10.638%	$205.4769	$205.48	$205.50	$205.50
Purchase #5	$158.72	6.421%	$168.9114	$168.91	$168.90	$168.90
Purchase #6	$122.87	5.549%	$129.6881	$129.69	$129.70	$129.70
Purchase #7	$121.44	5.689%	$128.3487	$128.35	$128.35	$128.30
7 purchase totals =	$1,092.05		$1,182.4887	$1,182.50	$1,182.50	$1,182.50