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	$166.45	12.404%	$187.0965	$187.10	$187.10	$187.10
Purchase #2	$142.58	3.350%	$147.3564	$147.36	$147.35	$147.40
Purchase #3	$144.59	5.660%	$152.7738	$152.77	$152.75	$152.80
Purchase #4	$234.54	5.803%	$248.1504	$248.15	$248.15	$248.20
Purchase #5	$63.94	12.574%	$71.9798	$71.98	$72.00	$72.00
Purchase #6	$141.35	7.783%	$152.3513	$152.35	$152.35	$152.40
Purchase #7	$48.70	7.412%	$52.3096	$52.31	$52.30	$52.30
7 purchase totals =	$942.15		$1,012.0178	$1,012.02	$1,012.00	$1,012.20