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	$77.39	5.767%	$81.8531	$81.85	$81.85	$81.90
Purchase #2	$11.48	4.506%	$11.9973	$12.00	$12.00	$12.00
Purchase #3	$98.88	12.162%	$110.9058	$110.91	$110.90	$110.90
Purchase #4	$127.32	8.324%	$137.9181	$137.92	$137.90	$137.90
Purchase #5	$228.94	6.216%	$243.1709	$243.17	$243.15	$243.20
Purchase #6	$159.46	5.620%	$168.4217	$168.42	$168.40	$168.40
Purchase #7	$96.25	5.503%	$101.5466	$101.55	$101.55	$101.50
7 purchase totals =	$799.72		$855.8135	$855.82	$855.75	$855.80