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	$215.32	8.673%	$233.9947	$233.99	$234.00	$234.00
Purchase #2	$148.43	13.584%	$168.5927	$168.59	$168.60	$168.60
Purchase #3	$49.48	8.165%	$53.52	$53.52	$53.50	$53.50
Purchase #4	$107.45	3.682%	$111.4063	$111.41	$111.40	$111.40
Purchase #5	$247.48	6.362%	$263.2247	$263.22	$263.20	$263.20
Purchase #6	$77.69	9.706%	$85.2306	$85.23	$85.25	$85.20
Purchase #7	$182.75	4.557%	$191.0779	$191.08	$191.10	$191.10
7 purchase totals =	$1,028.60		$1,107.0469	$1,107.04	$1,107.05	$1,107.00