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	$143.48	11.121%	$159.4364	$159.44	$159.45	$159.40
Purchase #2	$248.55	6.618%	$264.999	$265.00	$265.00	$265.00
Purchase #3	$24.74	3.224%	$25.5376	$25.54	$25.55	$25.50
Purchase #4	$95.90	4.553%	$100.2663	$100.27	$100.25	$100.30
Purchase #5	$119.91	9.539%	$131.3482	$131.35	$131.35	$131.30
Purchase #6	$238.64	10.494%	$263.6829	$263.68	$263.70	$263.70
Purchase #7	$110.63	11.702%	$123.5759	$123.58	$123.60	$123.60
7 purchase totals =	$981.85		$1,068.8463	$1,068.86	$1,068.90	$1,068.80