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	$157.95	10.732%	$174.9012	$174.90	$174.90	$174.90
Purchase #2	$216.90	12.819%	$244.7044	$244.70	$244.70	$244.70
Purchase #3	$141.26	9.309%	$154.4099	$154.41	$154.40	$154.40
Purchase #4	$27.45	4.195%	$28.6015	$28.60	$28.60	$28.60
Purchase #5	$209.83	3.288%	$216.7292	$216.73	$216.75	$216.70
Purchase #6	$24.61	10.687%	$27.2401	$27.24	$27.25	$27.20
Purchase #7	$172.80	13.851%	$196.7345	$196.73	$196.75	$196.70
7 purchase totals =	$950.80		$1,043.3208	$1,043.31	$1,043.35	$1,043.20