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	$152.91	10.356%	$168.7454	$168.75	$168.75	$168.70
Purchase #2	$55.96	5.781%	$59.195	$59.20	$59.20	$59.20
Purchase #3	$130.38	12.679%	$146.9109	$146.91	$146.90	$146.90
Purchase #4	$237.83	4.324%	$248.1138	$248.11	$248.10	$248.10
Purchase #5	$130.92	10.134%	$144.1874	$144.19	$144.20	$144.20
Purchase #6	$144.69	3.762%	$150.1332	$150.13	$150.15	$150.10
Purchase #7	$170.54	9.115%	$186.0847	$186.08	$186.10	$186.10
7 purchase totals =	$1,023.23		$1,103.3704	$1,103.37	$1,103.40	$1,103.30