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	$230.62	8.451%	$250.1097	$250.11	$250.10	$250.10
Purchase #2	$189.52	3.593%	$196.3295	$196.33	$196.35	$196.30
Purchase #3	$97.60	11.823%	$109.1392	$109.14	$109.15	$109.10
Purchase #4	$164.78	13.524%	$187.0648	$187.06	$187.05	$187.10
Purchase #5	$163.46	4.511%	$170.8337	$170.83	$170.85	$170.80
Purchase #6	$241.99	9.258%	$264.3934	$264.39	$264.40	$264.40
Purchase #7	$122.79	6.433%	$130.6891	$130.69	$130.70	$130.70
7 purchase totals =	$1,210.76		$1,308.5594	$1,308.55	$1,308.60	$1,308.50