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	$196.83	3.373%	$203.4691	$203.47	$203.45	$203.50
Purchase #2	$173.48	13.108%	$196.2198	$196.22	$196.20	$196.20
Purchase #3	$42.34	11.419%	$47.1748	$47.17	$47.15	$47.20
Purchase #4	$91.83	7.104%	$98.3536	$98.35	$98.35	$98.40
Purchase #5	$99.28	13.870%	$113.0501	$113.05	$113.05	$113.10
Purchase #6	$186.82	11.112%	$207.5794	$207.58	$207.60	$207.60
Purchase #7	$157.80	5.539%	$166.5405	$166.54	$166.55	$166.50
7 purchase totals =	$948.38		$1,032.3873	$1,032.38	$1,032.35	$1,032.50