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	$53.98	4.171%	$56.2315	$56.23	$56.25	$56.20
Purchase #2	$229.41	11.104%	$254.8837	$254.88	$254.90	$254.90
Purchase #3	$198.88	6.490%	$211.7873	$211.79	$211.80	$211.80
Purchase #4	$184.85	8.705%	$200.9412	$200.94	$200.95	$200.90
Purchase #5	$13.74	3.840%	$14.2676	$14.27	$14.25	$14.30
Purchase #6	$216.52	13.351%	$245.4276	$245.43	$245.45	$245.40
Purchase #7	$27.97	4.705%	$29.286	$29.29	$29.30	$29.30
7 purchase totals =	$925.35		$1,012.8249	$1,012.83	$1,012.90	$1,012.80