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	$43.59	3.608%	$45.1627	$45.16	$45.15	$45.20
Purchase #2	$95.41	7.715%	$102.7709	$102.77	$102.75	$102.80
Purchase #3	$56.90	5.218%	$59.869	$59.87	$59.85	$59.90
Purchase #4	$172.39	8.333%	$186.7553	$186.76	$186.75	$186.80
Purchase #5	$70.86	8.399%	$76.8115	$76.81	$76.80	$76.80
Purchase #6	$101.97	7.818%	$109.942	$109.94	$109.95	$109.90
Purchase #7	$41.77	5.676%	$44.1409	$44.14	$44.15	$44.10
7 purchase totals =	$582.89		$625.4523	$625.45	$625.40	$625.50