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	$140.88	9.544%	$154.3256	$154.33	$154.35	$154.30
Purchase #2	$80.27	13.454%	$91.0695	$91.07	$91.05	$91.10
Purchase #3	$163.29	7.530%	$175.5857	$175.59	$175.60	$175.60
Purchase #4	$19.82	13.666%	$22.5286	$22.53	$22.55	$22.50
Purchase #5	$96.88	13.280%	$109.7457	$109.75	$109.75	$109.70
Purchase #6	$50.73	5.233%	$53.3847	$53.38	$53.40	$53.40
Purchase #7	$19.46	3.635%	$20.1674	$20.17	$20.15	$20.20
7 purchase totals =	$571.33		$626.8072	$626.82	$626.85	$626.80