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	$176.91	6.858%	$189.0425	$189.04	$189.05	$189.00
Purchase #2	$20.78	7.270%	$22.2907	$22.29	$22.30	$22.30
Purchase #3	$224.77	3.168%	$231.8907	$231.89	$231.90	$231.90
Purchase #4	$98.79	5.294%	$104.0199	$104.02	$104.00	$104.00
Purchase #5	$141.64	12.243%	$158.981	$158.98	$159.00	$159.00
Purchase #6	$200.61	7.629%	$215.9145	$215.91	$215.90	$215.90
Purchase #7	$161.69	4.333%	$168.696	$168.70	$168.70	$168.70
7 purchase totals =	$1,025.19		$1,090.8353	$1,090.83	$1,090.85	$1,090.80