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	$128.69	10.420%	$142.0995	$142.10	$142.10	$142.10
Purchase #2	$58.77	12.182%	$65.9294	$65.93	$65.95	$65.90
Purchase #3	$235.98	7.787%	$254.3558	$254.36	$254.35	$254.40
Purchase #4	$48.70	3.352%	$50.3324	$50.33	$50.35	$50.30
Purchase #5	$173.57	4.505%	$181.3893	$181.39	$181.40	$181.40
Purchase #6	$190.57	3.156%	$196.5844	$196.58	$196.60	$196.60
Purchase #7	$35.33	8.425%	$38.3066	$38.31	$38.30	$38.30
7 purchase totals =	$871.61		$928.9974	$929.00	$929.05	$929.00