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	$119.44	13.174%	$135.175	$135.18	$135.20	$135.20
Purchase #2	$28.91	12.117%	$32.413	$32.41	$32.40	$32.40
Purchase #3	$69.90	12.609%	$78.7137	$78.71	$78.70	$78.70
Purchase #4	$131.56	8.144%	$142.2742	$142.27	$142.25	$142.30
Purchase #5	$196.57	4.447%	$205.3115	$205.31	$205.30	$205.30
Purchase #6	$210.40	10.336%	$232.1469	$232.15	$232.15	$232.10
Purchase #7	$157.49	13.736%	$179.1228	$179.12	$179.10	$179.10
7 purchase totals =	$914.27		$1,005.1571	$1,005.15	$1,005.10	$1,005.10