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	$218.83	11.264%	$243.479	$243.48	$243.50	$243.50
Purchase #2	$74.31	6.143%	$78.8749	$78.87	$78.85	$78.90
Purchase #3	$166.76	4.667%	$174.5427	$174.54	$174.55	$174.50
Purchase #4	$178.45	5.106%	$187.5617	$187.56	$187.55	$187.60
Purchase #5	$7.86	4.461%	$8.2106	$8.21	$8.20	$8.20
Purchase #6	$178.79	12.221%	$200.6399	$200.64	$200.65	$200.60
Purchase #7	$205.91	13.603%	$233.9199	$233.92	$233.90	$233.90
7 purchase totals =	$1,030.91		$1,127.2287	$1,127.22	$1,127.20	$1,127.20