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	$67.84	7.626%	$73.0135	$73.01	$73.00	$73.00
Purchase #2	$194.54	8.186%	$210.465	$210.47	$210.45	$210.50
Purchase #3	$235.78	7.673%	$253.8714	$253.87	$253.85	$253.90
Purchase #4	$46.59	8.121%	$50.3736	$50.37	$50.35	$50.40
Purchase #5	$183.50	12.627%	$206.6705	$206.67	$206.65	$206.70
Purchase #6	$136.46	6.146%	$144.8468	$144.85	$144.85	$144.80
Purchase #7	$138.80	6.118%	$147.2918	$147.29	$147.30	$147.30
7 purchase totals =	$1,003.51		$1,086.5326	$1,086.53	$1,086.45	$1,086.60