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	$60.26	8.538%	$65.405	$65.41	$65.40	$65.40
Purchase #2	$78.92	6.797%	$84.2842	$84.28	$84.30	$84.30
Purchase #3	$43.32	10.542%	$47.8868	$47.89	$47.90	$47.90
Purchase #4	$96.25	8.841%	$104.7595	$104.76	$104.75	$104.80
Purchase #5	$135.70	11.695%	$151.5701	$151.57	$151.55	$151.60
Purchase #6	$97.73	11.534%	$109.0022	$109.00	$109.00	$109.00
Purchase #7	$99.59	11.852%	$111.3934	$111.39	$111.40	$111.40
7 purchase totals =	$611.77		$674.3012	$674.30	$674.30	$674.40