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	$175.58	6.725%	$187.3878	$187.39	$187.40	$187.40
Purchase #2	$92.84	6.758%	$99.1141	$99.11	$99.10	$99.10
Purchase #3	$148.87	4.731%	$155.913	$155.91	$155.90	$155.90
Purchase #4	$155.65	4.417%	$162.5251	$162.53	$162.55	$162.50
Purchase #5	$160.80	9.705%	$176.4056	$176.41	$176.40	$176.40
Purchase #6	$6.61	7.731%	$7.121	$7.12	$7.10	$7.10
Purchase #7	$164.53	12.721%	$185.4599	$185.46	$185.45	$185.50
7 purchase totals =	$904.88		$973.9265	$973.93	$973.90	$973.90