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	$78.96	10.558%	$87.2966	$87.30	$87.30	$87.30
Purchase #2	$212.35	3.275%	$219.3045	$219.30	$219.30	$219.30
Purchase #3	$235.34	10.654%	$260.4131	$260.41	$260.40	$260.40
Purchase #4	$122.61	4.288%	$127.8675	$127.87	$127.85	$127.90
Purchase #5	$200.85	11.332%	$223.6103	$223.61	$223.60	$223.60
Purchase #6	$72.96	10.349%	$80.5106	$80.51	$80.50	$80.50
Purchase #7	$104.48	11.188%	$116.1692	$116.17	$116.15	$116.20
7 purchase totals =	$1,027.55		$1,115.1718	$1,115.17	$1,115.10	$1,115.20