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	$132.64	13.817%	$150.9669	$150.97	$150.95	$151.00
Purchase #2	$178.34	6.404%	$189.7609	$189.76	$189.75	$189.80
Purchase #3	$142.72	6.584%	$152.1167	$152.12	$152.10	$152.10
Purchase #4	$81.56	3.222%	$84.1879	$84.19	$84.20	$84.20
Purchase #5	$171.88	11.370%	$191.4228	$191.42	$191.40	$191.40
Purchase #6	$75.98	5.108%	$79.8611	$79.86	$79.85	$79.90
Purchase #7	$219.53	8.523%	$238.2405	$238.24	$238.25	$238.20
7 purchase totals =	$1,002.65		$1,086.5568	$1,086.56	$1,086.50	$1,086.60