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	$67.41	5.414%	$71.0596	$71.06	$71.05	$71.10
Purchase #2	$69.74	4.769%	$73.0659	$73.07	$73.05	$73.10
Purchase #3	$125.38	13.740%	$142.6072	$142.61	$142.60	$142.60
Purchase #4	$242.39	5.464%	$255.6342	$255.63	$255.65	$255.60
Purchase #5	$238.74	4.108%	$248.5474	$248.55	$248.55	$248.50
Purchase #6	$70.72	4.328%	$73.7808	$73.78	$73.80	$73.80
Purchase #7	$93.86	6.449%	$99.913	$99.91	$99.90	$99.90
7 purchase totals =	$908.24		$964.6081	$964.61	$964.60	$964.60