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	$81.29	3.619%	$84.2319	$84.23	$84.25	$84.20
Purchase #2	$203.69	9.694%	$223.4357	$223.44	$223.45	$223.40
Purchase #3	$66.92	9.752%	$73.446	$73.45	$73.45	$73.40
Purchase #4	$234.56	6.439%	$249.6633	$249.66	$249.65	$249.70
Purchase #5	$168.27	7.732%	$181.2806	$181.28	$181.30	$181.30
Purchase #6	$78.27	6.727%	$83.5352	$83.54	$83.55	$83.50
Purchase #7	$148.73	13.332%	$168.5587	$168.56	$168.55	$168.60
7 purchase totals =	$981.73		$1,064.1514	$1,064.16	$1,064.20	$1,064.10