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	$67.68	9.187%	$73.8978	$73.90	$73.90	$73.90
Purchase #2	$211.98	5.210%	$223.0242	$223.02	$223.00	$223.00
Purchase #3	$246.92	10.454%	$272.733	$272.73	$272.75	$272.70
Purchase #4	$237.56	11.398%	$264.6371	$264.64	$264.65	$264.60
Purchase #5	$155.83	6.798%	$166.4233	$166.42	$166.40	$166.40
Purchase #6	$185.65	5.798%	$196.414	$196.41	$196.40	$196.40
Purchase #7	$51.84	13.575%	$58.8773	$58.88	$58.90	$58.90
7 purchase totals =	$1,157.46		$1,256.0067	$1,256.00	$1,256.00	$1,255.90