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	$119.74	3.470%	$123.895	$123.90	$123.90	$123.90
Purchase #2	$191.83	4.687%	$200.8211	$200.82	$200.80	$200.80
Purchase #3	$27.53	5.226%	$28.9687	$28.97	$28.95	$29.00
Purchase #4	$91.73	12.847%	$103.5146	$103.51	$103.50	$103.50
Purchase #5	$233.68	6.280%	$248.3551	$248.36	$248.35	$248.40
Purchase #6	$64.90	7.643%	$69.8603	$69.86	$69.85	$69.90
Purchase #7	$116.54	3.432%	$120.5397	$120.54	$120.55	$120.50
7 purchase totals =	$845.95		$895.9545	$895.96	$895.90	$896.00