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	$170.90	8.859%	$186.04	$186.04	$186.05	$186.00
Purchase #2	$51.53	7.619%	$55.4561	$55.46	$55.45	$55.50
Purchase #3	$141.89	7.522%	$152.563	$152.56	$152.55	$152.60
Purchase #4	$21.48	11.826%	$24.0202	$24.02	$24.00	$24.00
Purchase #5	$165.71	5.279%	$174.4578	$174.46	$174.45	$174.50
Purchase #6	$248.33	10.469%	$274.3277	$274.33	$274.35	$274.30
Purchase #7	$54.99	8.503%	$59.6658	$59.67	$59.65	$59.70
7 purchase totals =	$854.83		$926.5306	$926.54	$926.50	$926.60