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	$46.82	7.705%	$50.4275	$50.43	$50.45	$50.40
Purchase #2	$198.43	5.785%	$209.9092	$209.91	$209.90	$209.90
Purchase #3	$63.83	13.740%	$72.6002	$72.60	$72.60	$72.60
Purchase #4	$49.80	5.540%	$52.5589	$52.56	$52.55	$52.60
Purchase #5	$64.97	12.676%	$73.2056	$73.21	$73.20	$73.20
Purchase #6	$164.93	5.866%	$174.6048	$174.60	$174.60	$174.60
Purchase #7	$58.83	6.871%	$62.8722	$62.87	$62.85	$62.90
7 purchase totals =	$647.61		$696.1784	$696.18	$696.15	$696.20