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	$5.28	3.327%	$5.4557	$5.46	$5.45	$5.50
Purchase #2	$61.41	5.765%	$64.9503	$64.95	$64.95	$65.00
Purchase #3	$199.54	3.416%	$206.3563	$206.36	$206.35	$206.40
Purchase #4	$217.42	13.851%	$247.5348	$247.53	$247.55	$247.50
Purchase #5	$172.83	13.780%	$196.646	$196.65	$196.65	$196.60
Purchase #6	$174.41	6.570%	$185.8687	$185.87	$185.85	$185.90
Purchase #7	$183.66	11.299%	$204.4117	$204.41	$204.40	$204.40
7 purchase totals =	$1,014.55		$1,111.2235	$1,111.23	$1,111.20	$1,111.30