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	$111.98	4.839%	$117.3987	$117.40	$117.40	$117.40
Purchase #2	$162.78	13.831%	$185.2941	$185.29	$185.30	$185.30
Purchase #3	$58.33	6.377%	$62.0497	$62.05	$62.05	$62.00
Purchase #4	$31.63	13.243%	$35.8188	$35.82	$35.80	$35.80
Purchase #5	$33.89	10.839%	$37.5633	$37.56	$37.55	$37.60
Purchase #6	$58.82	6.747%	$62.7886	$62.79	$62.80	$62.80
Purchase #7	$94.88	4.556%	$99.2027	$99.20	$99.20	$99.20
7 purchase totals =	$552.31		$600.1159	$600.11	$600.10	$600.10