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	$92.33	3.282%	$95.3603	$95.36	$95.35	$95.40
Purchase #2	$65.32	12.652%	$73.5843	$73.58	$73.60	$73.60
Purchase #3	$209.30	3.296%	$216.1985	$216.20	$216.20	$216.20
Purchase #4	$73.71	12.734%	$83.0962	$83.10	$83.10	$83.10
Purchase #5	$56.96	9.594%	$62.4247	$62.42	$62.40	$62.40
Purchase #6	$23.27	10.518%	$25.7175	$25.72	$25.70	$25.70
Purchase #7	$72.93	7.623%	$78.4895	$78.49	$78.50	$78.50
7 purchase totals =	$593.82		$634.8710	$634.87	$634.85	$634.90