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	$110.98	11.449%	$123.6861	$123.69	$123.70	$123.70
Purchase #2	$168.47	13.341%	$190.9456	$190.95	$190.95	$190.90
Purchase #3	$191.63	10.130%	$211.0421	$211.04	$211.05	$211.00
Purchase #4	$155.89	3.222%	$160.9128	$160.91	$160.90	$160.90
Purchase #5	$210.61	10.811%	$233.379	$233.38	$233.40	$233.40
Purchase #6	$43.25	4.228%	$45.0786	$45.08	$45.10	$45.10
Purchase #7	$85.99	3.690%	$89.163	$89.16	$89.15	$89.20
7 purchase totals =	$966.82		$1,054.2072	$1,054.21	$1,054.25	$1,054.20