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	$95.83	4.396%	$100.0427	$100.04	$100.05	$100.00
Purchase #2	$66.66	3.594%	$69.0558	$69.06	$69.05	$69.10
Purchase #3	$243.32	13.647%	$276.5259	$276.53	$276.55	$276.50
Purchase #4	$206.50	8.214%	$223.4619	$223.46	$223.45	$223.50
Purchase #5	$109.56	7.860%	$118.1714	$118.17	$118.15	$118.20
Purchase #6	$182.91	3.195%	$188.754	$188.75	$188.75	$188.80
Purchase #7	$95.46	4.785%	$100.0278	$100.03	$100.05	$100.00
7 purchase totals =	$1,000.24		$1,076.0395	$1,076.04	$1,076.05	$1,076.10