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	$222.35	5.148%	$233.7966	$233.80	$233.80	$233.80
Purchase #2	$29.96	4.561%	$31.3265	$31.33	$31.35	$31.30
Purchase #3	$60.88	6.424%	$64.7909	$64.79	$64.80	$64.80
Purchase #4	$250.77	12.172%	$281.2937	$281.29	$281.30	$281.30
Purchase #5	$155.49	11.470%	$173.3247	$173.32	$173.30	$173.30
Purchase #6	$7.60	8.870%	$8.2741	$8.27	$8.25	$8.30
Purchase #7	$60.61	11.715%	$67.7105	$67.71	$67.70	$67.70
7 purchase totals =	$787.66		$860.5170	$860.51	$860.50	$860.50