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	$171.54	3.236%	$177.091	$177.09	$177.10	$177.10
Purchase #2	$164.78	3.735%	$170.9345	$170.93	$170.95	$170.90
Purchase #3	$68.76	3.539%	$71.1934	$71.19	$71.20	$71.20
Purchase #4	$12.94	6.870%	$13.829	$13.83	$13.85	$13.80
Purchase #5	$94.88	12.746%	$106.9734	$106.97	$106.95	$107.00
Purchase #6	$160.37	7.607%	$172.5693	$172.57	$172.55	$172.60
Purchase #7	$53.56	11.568%	$59.7558	$59.76	$59.75	$59.80
7 purchase totals =	$726.83		$772.3464	$772.34	$772.35	$772.40