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	$187.98	13.717%	$213.7652	$213.77	$213.75	$213.80
Purchase #2	$238.69	4.366%	$249.1112	$249.11	$249.10	$249.10
Purchase #3	$64.72	11.510%	$72.1693	$72.17	$72.15	$72.20
Purchase #4	$37.92	5.446%	$39.9851	$39.99	$40.00	$40.00
Purchase #5	$91.73	3.521%	$94.9598	$94.96	$94.95	$95.00
Purchase #6	$153.86	8.796%	$167.3935	$167.39	$167.40	$167.40
Purchase #7	$173.89	4.330%	$181.4194	$181.42	$181.40	$181.40
7 purchase totals =	$948.79		$1,018.8035	$1,018.81	$1,018.75	$1,018.90