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	$177.67	12.767%	$200.3531	$200.35	$200.35	$200.40
Purchase #2	$128.71	9.868%	$141.4111	$141.41	$141.40	$141.40
Purchase #3	$62.97	7.667%	$67.7979	$67.80	$67.80	$67.80
Purchase #4	$74.54	12.495%	$83.8538	$83.85	$83.85	$83.90
Purchase #5	$131.32	3.847%	$136.3719	$136.37	$136.35	$136.40
Purchase #6	$200.73	9.304%	$219.4059	$219.41	$219.40	$219.40
Purchase #7	$181.71	7.266%	$194.913	$194.91	$194.90	$194.90
7 purchase totals =	$957.65		$1,044.1067	$1,044.10	$1,044.05	$1,044.20