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	$243.92	11.124%	$271.0537	$271.05	$271.05	$271.10
Purchase #2	$91.50	5.635%	$96.656	$96.66	$96.65	$96.70
Purchase #3	$178.86	9.712%	$196.2309	$196.23	$196.25	$196.20
Purchase #4	$134.50	13.229%	$152.293	$152.29	$152.30	$152.30
Purchase #5	$177.59	7.383%	$190.7015	$190.70	$190.70	$190.70
Purchase #6	$105.32	7.408%	$113.1221	$113.12	$113.10	$113.10
Purchase #7	$102.82	8.232%	$111.2841	$111.28	$111.30	$111.30
7 purchase totals =	$1,034.51		$1,131.3413	$1,131.33	$1,131.35	$1,131.40