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	$188.69	5.254%	$198.6038	$198.60	$198.60	$198.60
Purchase #2	$191.78	13.826%	$218.2955	$218.30	$218.30	$218.30
Purchase #3	$65.86	6.573%	$70.189	$70.19	$70.20	$70.20
Purchase #4	$173.29	7.605%	$186.4687	$186.47	$186.45	$186.50
Purchase #5	$70.27	11.180%	$78.1262	$78.13	$78.15	$78.10
Purchase #6	$210.59	8.829%	$229.183	$229.18	$229.20	$229.20
Purchase #7	$203.30	12.233%	$228.1697	$228.17	$228.15	$228.20
7 purchase totals =	$1,103.78		$1,209.0359	$1,209.04	$1,209.05	$1,209.10