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	$240.54	5.498%	$253.7649	$253.76	$253.75	$253.80
Purchase #2	$54.57	12.780%	$61.544	$61.54	$61.55	$61.50
Purchase #3	$145.97	3.840%	$151.5752	$151.58	$151.60	$151.60
Purchase #4	$97.63	5.120%	$102.6287	$102.63	$102.65	$102.60
Purchase #5	$193.25	3.133%	$199.3045	$199.30	$199.30	$199.30
Purchase #6	$157.93	10.464%	$174.4558	$174.46	$174.45	$174.50
Purchase #7	$31.74	11.682%	$35.4479	$35.45	$35.45	$35.40
7 purchase totals =	$921.63		$978.7210	$978.72	$978.75	$978.70