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	$89.41	10.614%	$98.9	$98.90	$98.90	$98.90
Purchase #2	$218.76	11.238%	$243.3442	$243.34	$243.35	$243.30
Purchase #3	$222.98	10.163%	$245.6415	$245.64	$245.65	$245.60
Purchase #4	$131.58	9.649%	$144.2762	$144.28	$144.30	$144.30
Purchase #5	$119.98	4.276%	$125.1103	$125.11	$125.10	$125.10
Purchase #6	$98.47	7.583%	$105.937	$105.94	$105.95	$105.90
Purchase #7	$89.32	13.213%	$101.1219	$101.12	$101.10	$101.10
7 purchase totals =	$970.50		$1,064.3311	$1,064.33	$1,064.35	$1,064.20