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	$151.37	10.607%	$167.4258	$167.43	$167.45	$167.40
Purchase #2	$93.89	10.332%	$103.5907	$103.59	$103.60	$103.60
Purchase #3	$85.78	9.179%	$93.6537	$93.65	$93.65	$93.70
Purchase #4	$76.75	3.765%	$79.6396	$79.64	$79.65	$79.60
Purchase #5	$53.50	6.599%	$57.0305	$57.03	$57.05	$57.00
Purchase #6	$50.39	9.106%	$54.9785	$54.98	$55.00	$55.00
Purchase #7	$133.71	12.243%	$150.0801	$150.08	$150.10	$150.10
7 purchase totals =	$645.39		$706.3989	$706.40	$706.50	$706.40