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	$211.76	6.620%	$225.7785	$225.78	$225.80	$225.80
Purchase #2	$36.43	3.780%	$37.8071	$37.81	$37.80	$37.80
Purchase #3	$16.45	10.362%	$18.1545	$18.15	$18.15	$18.20
Purchase #4	$65.69	12.301%	$73.7705	$73.77	$73.75	$73.80
Purchase #5	$238.56	10.868%	$264.4867	$264.49	$264.50	$264.50
Purchase #6	$102.30	11.739%	$114.309	$114.31	$114.30	$114.30
Purchase #7	$5.73	6.639%	$6.1104	$6.11	$6.10	$6.10
7 purchase totals =	$676.92		$740.4167	$740.42	$740.40	$740.50