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	$77.39	12.107%	$86.7596	$86.76	$86.75	$86.80
Purchase #2	$201.96	13.622%	$229.471	$229.47	$229.45	$229.50
Purchase #3	$133.33	8.331%	$144.4377	$144.44	$144.45	$144.40
Purchase #4	$35.94	12.311%	$40.3646	$40.36	$40.35	$40.40
Purchase #5	$139.38	6.426%	$148.3366	$148.34	$148.35	$148.30
Purchase #6	$163.38	4.201%	$170.2436	$170.24	$170.25	$170.20
Purchase #7	$174.98	6.211%	$185.848	$185.85	$185.85	$185.80
7 purchase totals =	$926.36		$1,005.4611	$1,005.46	$1,005.45	$1,005.40