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	$91.93	11.218%	$102.2427	$102.24	$102.25	$102.20
Purchase #2	$128.97	6.507%	$137.3621	$137.36	$137.35	$137.40
Purchase #3	$155.72	4.243%	$162.3272	$162.33	$162.35	$162.30
Purchase #4	$229.79	3.607%	$238.0785	$238.08	$238.10	$238.10
Purchase #5	$89.88	12.265%	$100.9038	$100.90	$100.90	$100.90
Purchase #6	$99.57	8.367%	$107.901	$107.90	$107.90	$107.90
Purchase #7	$59.81	4.305%	$62.3848	$62.38	$62.40	$62.40
7 purchase totals =	$855.67		$911.2001	$911.19	$911.25	$911.20