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	$216.76	5.780%	$229.2887	$229.29	$229.30	$229.30
Purchase #2	$134.40	4.764%	$140.8028	$140.80	$140.80	$140.80
Purchase #3	$108.75	8.862%	$118.3874	$118.39	$118.40	$118.40
Purchase #4	$11.96	3.517%	$12.3806	$12.38	$12.40	$12.40
Purchase #5	$200.75	4.827%	$210.4402	$210.44	$210.45	$210.40
Purchase #6	$161.69	7.177%	$173.2945	$173.29	$173.30	$173.30
Purchase #7	$115.99	13.298%	$131.4144	$131.41	$131.40	$131.40
7 purchase totals =	$950.30		$1,016.0086	$1,016.00	$1,016.05	$1,016.00