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	$108.36	4.418%	$113.1473	$113.15	$113.15	$113.10
Purchase #2	$160.71	6.737%	$171.537	$171.54	$171.55	$171.50
Purchase #3	$26.59	4.688%	$27.8365	$27.84	$27.85	$27.80
Purchase #4	$162.73	10.712%	$180.1616	$180.16	$180.15	$180.20
Purchase #5	$49.80	10.453%	$55.0056	$55.01	$55.00	$55.00
Purchase #6	$231.34	11.553%	$258.0667	$258.07	$258.05	$258.10
Purchase #7	$201.69	6.159%	$214.1121	$214.11	$214.10	$214.10
7 purchase totals =	$941.22		$1,019.8668	$1,019.88	$1,019.85	$1,019.80