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	$58.61	8.444%	$63.559	$63.56	$63.55	$63.60
Purchase #2	$82.97	7.767%	$89.4143	$89.41	$89.40	$89.40
Purchase #3	$102.53	8.392%	$111.1343	$111.13	$111.15	$111.10
Purchase #4	$68.62	9.474%	$75.1211	$75.12	$75.10	$75.10
Purchase #5	$28.91	8.294%	$31.3078	$31.31	$31.30	$31.30
Purchase #6	$75.81	6.167%	$80.4852	$80.49	$80.50	$80.50
Purchase #7	$186.70	5.203%	$196.414	$196.41	$196.40	$196.40
7 purchase totals =	$604.15		$647.4357	$647.43	$647.40	$647.40