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	$179.70	9.220%	$196.2683	$196.27	$196.25	$196.30
Purchase #2	$78.50	7.420%	$84.3247	$84.32	$84.30	$84.30
Purchase #3	$202.48	3.239%	$209.0383	$209.04	$209.05	$209.00
Purchase #4	$77.88	3.728%	$80.7834	$80.78	$80.80	$80.80
Purchase #5	$17.83	10.785%	$19.753	$19.75	$19.75	$19.80
Purchase #6	$38.35	9.810%	$42.1121	$42.11	$42.10	$42.10
Purchase #7	$42.32	6.726%	$45.1664	$45.17	$45.15	$45.20
7 purchase totals =	$637.06		$677.4462	$677.44	$677.40	$677.50