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	$127.26	11.869%	$142.3645	$142.36	$142.35	$142.40
Purchase #2	$237.91	9.736%	$261.0729	$261.07	$261.05	$261.10
Purchase #3	$125.88	13.278%	$142.5943	$142.59	$142.60	$142.60
Purchase #4	$40.87	13.197%	$46.2636	$46.26	$46.25	$46.30
Purchase #5	$172.60	7.678%	$185.8522	$185.85	$185.85	$185.90
Purchase #6	$34.98	7.321%	$37.5409	$37.54	$37.55	$37.50
Purchase #7	$195.97	13.857%	$223.1256	$223.13	$223.15	$223.10
7 purchase totals =	$935.47		$1,038.8140	$1,038.80	$1,038.80	$1,038.90