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	$180.68	5.558%	$190.7222	$190.72	$190.70	$190.70
Purchase #2	$150.29	4.440%	$156.9629	$156.96	$156.95	$157.00
Purchase #3	$122.32	13.415%	$138.7292	$138.73	$138.75	$138.70
Purchase #4	$96.69	6.288%	$102.7699	$102.77	$102.75	$102.80
Purchase #5	$201.96	10.163%	$222.4852	$222.49	$222.50	$222.50
Purchase #6	$129.98	12.723%	$146.5174	$146.52	$146.50	$146.50
Purchase #7	$54.94	11.339%	$61.1696	$61.17	$61.15	$61.20
7 purchase totals =	$936.86		$1,019.3564	$1,019.36	$1,019.30	$1,019.40