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	$97.64	7.546%	$105.0079	$105.01	$105.00	$105.00
Purchase #2	$238.56	12.553%	$268.5064	$268.51	$268.50	$268.50
Purchase #3	$248.98	11.636%	$277.9513	$277.95	$277.95	$278.00
Purchase #4	$60.37	7.310%	$64.783	$64.78	$64.80	$64.80
Purchase #5	$223.32	4.623%	$233.6441	$233.64	$233.65	$233.60
Purchase #6	$237.82	11.672%	$265.5784	$265.58	$265.60	$265.60
Purchase #7	$72.74	13.218%	$82.3548	$82.35	$82.35	$82.40
7 purchase totals =	$1,179.43		$1,297.8259	$1,297.82	$1,297.85	$1,297.90