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	$156.80	12.116%	$175.7979	$175.80	$175.80	$175.80
Purchase #2	$106.53	6.746%	$113.7165	$113.72	$113.70	$113.70
Purchase #3	$120.36	9.505%	$131.8002	$131.80	$131.80	$131.80
Purchase #4	$227.69	12.153%	$255.3612	$255.36	$255.35	$255.40
Purchase #5	$46.93	7.432%	$50.4178	$50.42	$50.40	$50.40
Purchase #6	$167.80	10.234%	$184.9727	$184.97	$184.95	$185.00
Purchase #7	$162.79	13.799%	$185.2534	$185.25	$185.25	$185.30
7 purchase totals =	$988.90		$1,097.3197	$1,097.32	$1,097.25	$1,097.40