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	$242.28	6.809%	$258.7768	$258.78	$258.80	$258.80
Purchase #2	$147.35	3.242%	$152.1271	$152.13	$152.15	$152.10
Purchase #3	$96.55	8.687%	$104.9373	$104.94	$104.95	$104.90
Purchase #4	$231.69	13.133%	$262.1178	$262.12	$262.10	$262.10
Purchase #5	$23.91	6.579%	$25.483	$25.48	$25.50	$25.50
Purchase #6	$53.69	3.594%	$55.6196	$55.62	$55.60	$55.60
Purchase #7	$185.55	3.661%	$192.343	$192.34	$192.35	$192.30
7 purchase totals =	$981.02		$1,051.4046	$1,051.41	$1,051.45	$1,051.30