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	$174.81	6.449%	$186.0835	$186.08	$186.10	$186.10
Purchase #2	$108.71	6.807%	$116.1099	$116.11	$116.10	$116.10
Purchase #3	$45.42	10.164%	$50.0365	$50.04	$50.05	$50.00
Purchase #4	$50.61	13.426%	$57.4049	$57.40	$57.40	$57.40
Purchase #5	$72.99	7.190%	$78.238	$78.24	$78.25	$78.20
Purchase #6	$196.89	6.742%	$210.1643	$210.16	$210.15	$210.20
Purchase #7	$128.71	8.658%	$139.8537	$139.85	$139.85	$139.90
7 purchase totals =	$778.14		$837.8908	$837.88	$837.90	$837.90