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	$223.60	7.649%	$240.7032	$240.70	$240.70	$240.70
Purchase #2	$191.25	9.399%	$209.2256	$209.23	$209.25	$209.20
Purchase #3	$65.79	13.830%	$74.8888	$74.89	$74.90	$74.90
Purchase #4	$92.69	4.515%	$96.875	$96.88	$96.90	$96.90
Purchase #5	$201.69	8.402%	$218.636	$218.64	$218.65	$218.60
Purchase #6	$155.81	8.310%	$168.7578	$168.76	$168.75	$168.80
Purchase #7	$80.89	12.399%	$90.9196	$90.92	$90.90	$90.90
7 purchase totals =	$1,011.72		$1,100.0060	$1,100.02	$1,100.05	$1,100.00