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	$122.89	3.333%	$126.9859	$126.99	$127.00	$127.00
Purchase #2	$120.89	8.789%	$131.515	$131.52	$131.50	$131.50
Purchase #3	$51.33	11.744%	$57.3582	$57.36	$57.35	$57.40
Purchase #4	$175.40	5.812%	$185.5942	$185.59	$185.60	$185.60
Purchase #5	$39.55	12.308%	$44.4178	$44.42	$44.40	$44.40
Purchase #6	$184.67	8.539%	$200.439	$200.44	$200.45	$200.40
Purchase #7	$71.46	3.528%	$73.9811	$73.98	$74.00	$74.00
7 purchase totals =	$766.19		$820.2912	$820.30	$820.30	$820.30