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	$96.90	9.388%	$105.997	$106.00	$106.00	$106.00
Purchase #2	$193.94	10.274%	$213.8654	$213.87	$213.85	$213.90
Purchase #3	$184.26	6.751%	$196.6994	$196.70	$196.70	$196.70
Purchase #4	$127.53	9.625%	$139.8048	$139.80	$139.80	$139.80
Purchase #5	$114.56	10.461%	$126.5441	$126.54	$126.55	$126.50
Purchase #6	$197.41	13.152%	$223.3734	$223.37	$223.35	$223.40
Purchase #7	$63.49	10.464%	$70.1336	$70.13	$70.15	$70.10
7 purchase totals =	$978.09		$1,076.4177	$1,076.41	$1,076.40	$1,076.40