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	$97.72	4.846%	$102.4555	$102.46	$102.45	$102.50
Purchase #2	$26.70	3.701%	$27.6882	$27.69	$27.70	$27.70
Purchase #3	$141.63	7.632%	$152.4392	$152.44	$152.45	$152.40
Purchase #4	$204.56	13.109%	$231.3758	$231.38	$231.40	$231.40
Purchase #5	$178.70	12.283%	$200.6497	$200.65	$200.65	$200.60
Purchase #6	$26.98	7.319%	$28.9547	$28.95	$28.95	$29.00
Purchase #7	$85.71	4.368%	$89.4538	$89.45	$89.45	$89.50
7 purchase totals =	$762.00		$833.0169	$833.02	$833.05	$833.10