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	$237.83	4.320%	$248.1043	$248.10	$248.10	$248.10
Purchase #2	$209.68	4.408%	$218.9227	$218.92	$218.90	$218.90
Purchase #3	$94.38	7.794%	$101.736	$101.74	$101.75	$101.70
Purchase #4	$145.48	13.160%	$164.6252	$164.63	$164.65	$164.60
Purchase #5	$52.55	9.526%	$57.5559	$57.56	$57.55	$57.60
Purchase #6	$181.62	8.192%	$196.4983	$196.50	$196.50	$196.50
Purchase #7	$198.32	11.492%	$221.1109	$221.11	$221.10	$221.10
7 purchase totals =	$1,119.86		$1,208.5533	$1,208.56	$1,208.55	$1,208.50