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	$132.95	3.666%	$137.8239	$137.82	$137.80	$137.80
Purchase #2	$151.77	4.170%	$158.0988	$158.10	$158.10	$158.10
Purchase #3	$51.27	10.581%	$56.6949	$56.69	$56.70	$56.70
Purchase #4	$49.25	11.704%	$55.0142	$55.01	$55.00	$55.00
Purchase #5	$94.35	4.670%	$98.7561	$98.76	$98.75	$98.80
Purchase #6	$77.59	3.283%	$80.1373	$80.14	$80.15	$80.10
Purchase #7	$249.76	10.474%	$275.9199	$275.92	$275.90	$275.90
7 purchase totals =	$806.94		$862.4451	$862.44	$862.40	$862.40