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	$57.49	3.764%	$59.6539	$59.65	$59.65	$59.70
Purchase #2	$96.93	11.674%	$108.2456	$108.25	$108.25	$108.20
Purchase #3	$40.74	12.466%	$45.8186	$45.82	$45.80	$45.80
Purchase #4	$41.87	13.336%	$47.4538	$47.45	$47.45	$47.50
Purchase #5	$145.36	8.376%	$157.5354	$157.54	$157.55	$157.50
Purchase #6	$49.74	4.498%	$51.9773	$51.98	$52.00	$52.00
Purchase #7	$241.33	7.285%	$258.9109	$258.91	$258.90	$258.90
7 purchase totals =	$673.46		$729.5955	$729.60	$729.60	$729.60