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	$173.31	10.225%	$191.0309	$191.03	$191.05	$191.00
Purchase #2	$29.81	6.427%	$31.7259	$31.73	$31.75	$31.70
Purchase #3	$138.37	9.710%	$151.8057	$151.81	$151.80	$151.80
Purchase #4	$64.69	7.349%	$69.4441	$69.44	$69.45	$69.40
Purchase #5	$152.91	7.797%	$164.8324	$164.83	$164.85	$164.80
Purchase #6	$145.54	3.444%	$150.5524	$150.55	$150.55	$150.60
Purchase #7	$155.71	6.258%	$165.4543	$165.45	$165.45	$165.50
7 purchase totals =	$860.34		$924.8457	$924.84	$924.90	$924.80