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	$134.32	12.824%	$151.5452	$151.55	$151.55	$151.50
Purchase #2	$82.63	8.596%	$89.7329	$89.73	$89.75	$89.70
Purchase #3	$179.53	11.853%	$200.8097	$200.81	$200.80	$200.80
Purchase #4	$58.27	9.833%	$63.9997	$64.00	$64.00	$64.00
Purchase #5	$145.78	3.191%	$150.4318	$150.43	$150.45	$150.40
Purchase #6	$227.61	9.477%	$249.1806	$249.18	$249.20	$249.20
Purchase #7	$245.71	9.186%	$268.2809	$268.28	$268.30	$268.30
7 purchase totals =	$1,073.85		$1,173.9808	$1,173.98	$1,174.05	$1,173.90