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	$71.96	9.294%	$78.648	$78.65	$78.65	$78.60
Purchase #2	$131.53	8.815%	$143.1244	$143.12	$143.10	$143.10
Purchase #3	$238.73	5.273%	$251.3182	$251.32	$251.30	$251.30
Purchase #4	$145.34	9.870%	$159.6851	$159.69	$159.70	$159.70
Purchase #5	$41.44	4.498%	$43.304	$43.30	$43.30	$43.30
Purchase #6	$48.54	3.788%	$50.3787	$50.38	$50.40	$50.40
Purchase #7	$191.34	9.269%	$209.0753	$209.08	$209.10	$209.10
7 purchase totals =	$868.88		$935.5337	$935.54	$935.55	$935.50