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	$116.40	5.585%	$122.9009	$122.90	$122.90	$122.90
Purchase #2	$40.65	4.546%	$42.4979	$42.50	$42.50	$42.50
Purchase #3	$191.45	4.586%	$200.2299	$200.23	$200.25	$200.20
Purchase #4	$175.46	13.281%	$198.7628	$198.76	$198.75	$198.80
Purchase #5	$109.92	5.197%	$115.6325	$115.63	$115.65	$115.60
Purchase #6	$140.26	12.650%	$158.0029	$158.00	$158.00	$158.00
Purchase #7	$85.34	5.349%	$89.9048	$89.90	$89.90	$89.90
7 purchase totals =	$859.48		$927.9317	$927.92	$927.95	$927.90