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	$37.41	3.850%	$38.8503	$38.85	$38.85	$38.90
Purchase #2	$71.92	11.107%	$79.9082	$79.91	$79.90	$79.90
Purchase #3	$69.76	3.451%	$72.1674	$72.17	$72.15	$72.20
Purchase #4	$157.91	8.482%	$171.3039	$171.30	$171.30	$171.30
Purchase #5	$246.90	9.728%	$270.9184	$270.92	$270.90	$270.90
Purchase #6	$206.50	6.476%	$219.8729	$219.87	$219.85	$219.90
Purchase #7	$236.53	9.219%	$258.3357	$258.34	$258.35	$258.30
7 purchase totals =	$1,026.93		$1,111.3568	$1,111.36	$1,111.30	$1,111.40