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	$121.83	8.445%	$132.1185	$132.12	$132.10	$132.10
Purchase #2	$86.53	3.481%	$89.5421	$89.54	$89.55	$89.50
Purchase #3	$168.67	10.523%	$186.4191	$186.42	$186.40	$186.40
Purchase #4	$202.41	8.441%	$219.4954	$219.50	$219.50	$219.50
Purchase #5	$56.56	13.815%	$64.3738	$64.37	$64.35	$64.40
Purchase #6	$229.82	10.186%	$253.2295	$253.23	$253.25	$253.20
Purchase #7	$72.52	12.133%	$81.3189	$81.32	$81.30	$81.30
7 purchase totals =	$938.34		$1,026.4973	$1,026.50	$1,026.45	$1,026.40