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	$103.96	9.332%	$113.6615	$113.66	$113.65	$113.70
Purchase #2	$26.56	3.463%	$27.4798	$27.48	$27.50	$27.50
Purchase #3	$108.33	4.746%	$113.4713	$113.47	$113.45	$113.50
Purchase #4	$104.47	5.115%	$109.8136	$109.81	$109.80	$109.80
Purchase #5	$249.72	5.210%	$262.7304	$262.73	$262.75	$262.70
Purchase #6	$197.79	12.819%	$223.1447	$223.14	$223.15	$223.10
Purchase #7	$147.65	3.514%	$152.8384	$152.84	$152.85	$152.80
7 purchase totals =	$938.48		$1,003.1397	$1,003.13	$1,003.15	$1,003.10