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	$164.91	4.464%	$172.2716	$172.27	$172.25	$172.30
Purchase #2	$164.53	10.385%	$181.6164	$181.62	$181.60	$181.60
Purchase #3	$165.72	12.175%	$185.8964	$185.90	$185.90	$185.90
Purchase #4	$229.95	7.362%	$246.8789	$246.88	$246.90	$246.90
Purchase #5	$167.44	11.572%	$186.8162	$186.82	$186.80	$186.80
Purchase #6	$79.33	4.268%	$82.7158	$82.72	$82.70	$82.70
Purchase #7	$145.97	9.651%	$160.0576	$160.06	$160.05	$160.10
7 purchase totals =	$1,117.85		$1,216.2529	$1,216.27	$1,216.20	$1,216.30