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	$52.57	10.429%	$58.0525	$58.05	$58.05	$58.10
Purchase #2	$102.70	3.553%	$106.3489	$106.35	$106.35	$106.30
Purchase #3	$104.40	6.841%	$111.542	$111.54	$111.55	$111.50
Purchase #4	$238.35	13.391%	$270.2674	$270.27	$270.25	$270.30
Purchase #5	$207.71	9.240%	$226.9024	$226.90	$226.90	$226.90
Purchase #6	$198.61	12.148%	$222.7371	$222.74	$222.75	$222.70
Purchase #7	$61.52	3.740%	$63.8208	$63.82	$63.80	$63.80
7 purchase totals =	$965.86		$1,059.6711	$1,059.67	$1,059.65	$1,059.60