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	$52.72	9.135%	$57.536	$57.54	$57.55	$57.50
Purchase #2	$64.38	13.392%	$73.0018	$73.00	$73.00	$73.00
Purchase #3	$215.30	3.334%	$222.4781	$222.48	$222.50	$222.50
Purchase #4	$133.73	8.826%	$145.533	$145.53	$145.55	$145.50
Purchase #5	$169.58	3.345%	$175.2525	$175.25	$175.25	$175.30
Purchase #6	$84.82	5.134%	$89.1747	$89.17	$89.15	$89.20
Purchase #7	$167.88	3.476%	$173.7155	$173.72	$173.70	$173.70
7 purchase totals =	$888.41		$936.6916	$936.69	$936.70	$936.70