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	$176.26	7.261%	$189.0582	$189.06	$189.05	$189.10
Purchase #2	$77.95	5.732%	$82.4181	$82.42	$82.40	$82.40
Purchase #3	$84.65	13.215%	$95.8365	$95.84	$95.85	$95.80
Purchase #4	$17.84	13.816%	$20.3048	$20.30	$20.30	$20.30
Purchase #5	$48.90	13.253%	$55.3807	$55.38	$55.40	$55.40
Purchase #6	$139.72	5.141%	$146.903	$146.90	$146.90	$146.90
Purchase #7	$180.61	13.139%	$204.3403	$204.34	$204.35	$204.30
7 purchase totals =	$725.93		$794.2416	$794.24	$794.25	$794.20