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	$94.27	9.243%	$102.9834	$102.98	$103.00	$103.00
Purchase #2	$103.54	11.801%	$115.7588	$115.76	$115.75	$115.80
Purchase #3	$28.92	12.316%	$32.4818	$32.48	$32.50	$32.50
Purchase #4	$12.59	9.855%	$13.8307	$13.83	$13.85	$13.80
Purchase #5	$143.34	9.236%	$156.5789	$156.58	$156.60	$156.60
Purchase #6	$179.61	3.158%	$185.2821	$185.28	$185.30	$185.30
Purchase #7	$181.39	13.360%	$205.6237	$205.62	$205.60	$205.60
7 purchase totals =	$743.66		$812.5394	$812.53	$812.60	$812.60