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	$244.62	11.323%	$272.3183	$272.32	$272.30	$272.30
Purchase #2	$63.92	5.299%	$67.3071	$67.31	$67.30	$67.30
Purchase #3	$73.78	6.418%	$78.5152	$78.52	$78.50	$78.50
Purchase #4	$174.52	9.155%	$190.4973	$190.50	$190.50	$190.50
Purchase #5	$114.27	13.644%	$129.861	$129.86	$129.85	$129.90
Purchase #6	$73.57	12.492%	$82.7604	$82.76	$82.75	$82.80
Purchase #7	$202.61	13.398%	$229.7557	$229.76	$229.75	$229.80
7 purchase totals =	$947.29		$1,051.0150	$1,051.03	$1,050.95	$1,051.10