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	$122.27	8.872%	$133.1178	$133.12	$133.10	$133.10
Purchase #2	$184.82	6.445%	$196.7316	$196.73	$196.75	$196.70
Purchase #3	$109.27	12.623%	$123.0632	$123.06	$123.05	$123.10
Purchase #4	$79.45	12.830%	$89.6434	$89.64	$89.65	$89.60
Purchase #5	$181.95	6.295%	$193.4038	$193.40	$193.40	$193.40
Purchase #6	$238.70	9.714%	$261.8873	$261.89	$261.90	$261.90
Purchase #7	$145.43	13.116%	$164.5046	$164.50	$164.50	$164.50
7 purchase totals =	$1,061.89		$1,162.3517	$1,162.34	$1,162.35	$1,162.30