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	$67.65	6.754%	$72.2191	$72.22	$72.20	$72.20
Purchase #2	$241.41	12.566%	$271.7456	$271.75	$271.75	$271.70
Purchase #3	$181.81	9.206%	$198.5474	$198.55	$198.55	$198.50
Purchase #4	$90.45	4.148%	$94.2019	$94.20	$94.20	$94.20
Purchase #5	$141.74	9.573%	$155.3088	$155.31	$155.30	$155.30
Purchase #6	$172.93	5.214%	$181.9466	$181.95	$181.95	$181.90
Purchase #7	$123.74	13.513%	$140.461	$140.46	$140.45	$140.50
7 purchase totals =	$1,019.73		$1,114.4304	$1,114.44	$1,114.40	$1,114.30