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	$168.87	5.430%	$178.0396	$178.04	$178.05	$178.00
Purchase #2	$10.38	10.338%	$11.4531	$11.45	$11.45	$11.50
Purchase #3	$41.99	12.758%	$47.3471	$47.35	$47.35	$47.30
Purchase #4	$73.53	11.731%	$82.1558	$82.16	$82.15	$82.20
Purchase #5	$162.26	5.853%	$171.7571	$171.76	$171.75	$171.80
Purchase #6	$74.89	4.386%	$78.1747	$78.17	$78.15	$78.20
Purchase #7	$59.67	7.438%	$64.1083	$64.11	$64.10	$64.10
7 purchase totals =	$591.59		$633.0357	$633.04	$633.00	$633.10