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	$155.33	4.468%	$162.2701	$162.27	$162.25	$162.30
Purchase #2	$134.37	11.836%	$150.274	$150.27	$150.25	$150.30
Purchase #3	$244.66	7.850%	$263.8658	$263.87	$263.85	$263.90
Purchase #4	$143.91	8.430%	$156.0416	$156.04	$156.05	$156.00
Purchase #5	$208.98	9.692%	$229.2343	$229.23	$229.25	$229.20
Purchase #6	$120.97	3.506%	$125.2112	$125.21	$125.20	$125.20
Purchase #7	$90.32	11.451%	$100.6625	$100.66	$100.65	$100.70
7 purchase totals =	$1,098.54		$1,187.5595	$1,187.55	$1,187.50	$1,187.60