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	$78.49	10.159%	$86.4638	$86.46	$86.45	$86.50
Purchase #2	$175.87	11.752%	$196.5382	$196.54	$196.55	$196.50
Purchase #3	$87.73	12.869%	$99.02	$99.02	$99.00	$99.00
Purchase #4	$188.38	10.666%	$208.4726	$208.47	$208.45	$208.50
Purchase #5	$73.94	4.732%	$77.4388	$77.44	$77.45	$77.40
Purchase #6	$121.26	10.121%	$133.5327	$133.53	$133.55	$133.50
Purchase #7	$194.86	13.774%	$221.7	$221.70	$221.70	$221.70
7 purchase totals =	$920.53		$1,023.1661	$1,023.16	$1,023.15	$1,023.10