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	$232.73	9.193%	$254.1249	$254.12	$254.10	$254.10
Purchase #2	$174.54	7.726%	$188.025	$188.03	$188.05	$188.00
Purchase #3	$92.76	13.793%	$105.5544	$105.55	$105.55	$105.60
Purchase #4	$47.51	5.351%	$50.0523	$50.05	$50.05	$50.10
Purchase #5	$79.75	5.817%	$84.3891	$84.39	$84.40	$84.40
Purchase #6	$40.52	5.580%	$42.781	$42.78	$42.80	$42.80
Purchase #7	$241.59	11.119%	$268.4524	$268.45	$268.45	$268.50
7 purchase totals =	$909.40		$993.3791	$993.37	$993.40	$993.50