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	$140.89	4.243%	$146.868	$146.87	$146.85	$146.90
Purchase #2	$80.95	11.782%	$90.4875	$90.49	$90.50	$90.50
Purchase #3	$140.91	5.783%	$149.0588	$149.06	$149.05	$149.10
Purchase #4	$28.40	9.174%	$31.0054	$31.01	$31.00	$31.00
Purchase #5	$79.92	11.500%	$89.1108	$89.11	$89.10	$89.10
Purchase #6	$45.43	3.433%	$46.9896	$46.99	$47.00	$47.00
Purchase #7	$142.93	7.371%	$153.4654	$153.47	$153.45	$153.50
7 purchase totals =	$659.43		$706.9855	$707.00	$706.95	$707.10