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	$238.36	6.563%	$254.0036	$254.00	$254.00	$254.00
Purchase #2	$83.82	7.232%	$89.8819	$89.88	$89.90	$89.90
Purchase #3	$57.29	12.729%	$64.5824	$64.58	$64.60	$64.60
Purchase #4	$140.64	3.708%	$145.8549	$145.85	$145.85	$145.90
Purchase #5	$140.96	12.607%	$158.7308	$158.73	$158.75	$158.70
Purchase #6	$96.61	7.577%	$103.9301	$103.93	$103.95	$103.90
Purchase #7	$239.74	10.226%	$264.2558	$264.26	$264.25	$264.30
7 purchase totals =	$997.42		$1,081.2395	$1,081.23	$1,081.30	$1,081.30