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	$237.77	12.622%	$267.7813	$267.78	$267.80	$267.80
Purchase #2	$100.39	8.645%	$109.0687	$109.07	$109.05	$109.10
Purchase #3	$49.36	12.789%	$55.6727	$55.67	$55.65	$55.70
Purchase #4	$222.61	7.148%	$238.5222	$238.52	$238.50	$238.50
Purchase #5	$225.69	5.779%	$238.7326	$238.73	$238.75	$238.70
Purchase #6	$89.67	11.717%	$100.1766	$100.18	$100.20	$100.20
Purchase #7	$181.31	6.687%	$193.4342	$193.43	$193.45	$193.40
7 purchase totals =	$1,106.80		$1,203.3883	$1,203.38	$1,203.40	$1,203.40