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	$106.64	11.705%	$119.1222	$119.12	$119.10	$119.10
Purchase #2	$248.98	5.596%	$262.9129	$262.91	$262.90	$262.90
Purchase #3	$20.82	11.696%	$23.2551	$23.26	$23.25	$23.30
Purchase #4	$202.61	4.303%	$211.3283	$211.33	$211.35	$211.30
Purchase #5	$99.63	11.687%	$111.2738	$111.27	$111.25	$111.30
Purchase #6	$39.71	5.763%	$41.9985	$42.00	$42.00	$42.00
Purchase #7	$175.96	5.839%	$186.2343	$186.23	$186.25	$186.20
7 purchase totals =	$894.35		$956.1251	$956.12	$956.10	$956.10