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	$173.75	6.744%	$185.4677	$185.47	$185.45	$185.50
Purchase #2	$25.73	5.233%	$27.0765	$27.08	$27.10	$27.10
Purchase #3	$233.33	11.616%	$260.4336	$260.43	$260.45	$260.40
Purchase #4	$44.75	4.263%	$46.6577	$46.66	$46.65	$46.70
Purchase #5	$58.54	12.102%	$65.6245	$65.62	$65.60	$65.60
Purchase #6	$75.82	3.260%	$78.2917	$78.29	$78.30	$78.30
Purchase #7	$55.96	10.181%	$61.6573	$61.66	$61.65	$61.70
7 purchase totals =	$667.88		$725.2090	$725.21	$725.20	$725.30