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	$159.69	9.533%	$174.9132	$174.91	$174.90	$174.90
Purchase #2	$210.51	10.792%	$233.2282	$233.23	$233.25	$233.20
Purchase #3	$37.64	8.618%	$40.8838	$40.88	$40.90	$40.90
Purchase #4	$63.28	11.405%	$70.4971	$70.50	$70.50	$70.50
Purchase #5	$207.27	7.290%	$222.38	$222.38	$222.40	$222.40
Purchase #6	$209.59	6.368%	$222.9367	$222.94	$222.95	$222.90
Purchase #7	$155.34	3.201%	$160.3124	$160.31	$160.30	$160.30
7 purchase totals =	$1,043.32		$1,125.1514	$1,125.15	$1,125.20	$1,125.10