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	$91.98	4.724%	$96.3251	$96.33	$96.35	$96.30
Purchase #2	$147.81	13.627%	$167.9521	$167.95	$167.95	$168.00
Purchase #3	$98.61	4.834%	$103.3768	$103.38	$103.40	$103.40
Purchase #4	$228.42	4.502%	$238.7035	$238.70	$238.70	$238.70
Purchase #5	$95.34	4.661%	$99.7838	$99.78	$99.80	$99.80
Purchase #6	$131.40	12.853%	$148.2888	$148.29	$148.30	$148.30
Purchase #7	$48.65	6.335%	$51.732	$51.73	$51.75	$51.70
7 purchase totals =	$842.21		$906.1621	$906.16	$906.25	$906.20