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	$81.26	5.135%	$85.4327	$85.43	$85.45	$85.40
Purchase #2	$49.61	11.761%	$55.4446	$55.44	$55.45	$55.40
Purchase #3	$173.91	9.111%	$189.7549	$189.75	$189.75	$189.80
Purchase #4	$51.60	6.337%	$54.8699	$54.87	$54.85	$54.90
Purchase #5	$178.25	4.166%	$185.6759	$185.68	$185.70	$185.70
Purchase #6	$89.77	9.503%	$98.3008	$98.30	$98.30	$98.30
Purchase #7	$50.36	3.533%	$52.1392	$52.14	$52.15	$52.10
7 purchase totals =	$674.76		$721.6180	$721.61	$721.65	$721.60