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	$106.98	10.398%	$118.1038	$118.10	$118.10	$118.10
Purchase #2	$100.33	7.494%	$107.8487	$107.85	$107.85	$107.80
Purchase #3	$71.98	9.265%	$78.6489	$78.65	$78.65	$78.60
Purchase #4	$184.93	6.728%	$197.3721	$197.37	$197.35	$197.40
Purchase #5	$115.79	10.386%	$127.8159	$127.82	$127.80	$127.80
Purchase #6	$63.78	6.184%	$67.7242	$67.72	$67.70	$67.70
Purchase #7	$169.91	9.404%	$185.8883	$185.89	$185.90	$185.90
7 purchase totals =	$813.70		$883.4019	$883.40	$883.35	$883.30