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	$31.27	11.751%	$34.9445	$34.94	$34.95	$34.90
Purchase #2	$230.47	5.116%	$242.2608	$242.26	$242.25	$242.30
Purchase #3	$115.78	10.314%	$127.7215	$127.72	$127.70	$127.70
Purchase #4	$33.36	13.664%	$37.9183	$37.92	$37.90	$37.90
Purchase #5	$71.80	3.226%	$74.1163	$74.12	$74.10	$74.10
Purchase #6	$209.82	3.580%	$217.3316	$217.33	$217.35	$217.30
Purchase #7	$53.64	6.730%	$57.25	$57.25	$57.25	$57.30
7 purchase totals =	$746.14		$791.5430	$791.54	$791.50	$791.50