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	$148.85	12.305%	$167.166	$167.17	$167.15	$167.20
Purchase #2	$173.92	8.814%	$189.2493	$189.25	$189.25	$189.20
Purchase #3	$147.71	13.426%	$167.5415	$167.54	$167.55	$167.50
Purchase #4	$164.60	13.310%	$186.5083	$186.51	$186.50	$186.50
Purchase #5	$151.72	3.407%	$156.8891	$156.89	$156.90	$156.90
Purchase #6	$67.73	8.866%	$73.7349	$73.73	$73.75	$73.70
Purchase #7	$156.69	12.139%	$175.7106	$175.71	$175.70	$175.70
7 purchase totals =	$1,011.22		$1,116.7997	$1,116.80	$1,116.80	$1,116.70