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	$150.35	9.448%	$164.5551	$164.56	$164.55	$164.60
Purchase #2	$83.53	5.671%	$88.267	$88.27	$88.25	$88.30
Purchase #3	$151.71	8.818%	$165.0878	$165.09	$165.10	$165.10
Purchase #4	$200.72	3.525%	$207.7954	$207.80	$207.80	$207.80
Purchase #5	$75.28	13.351%	$85.3306	$85.33	$85.35	$85.30
Purchase #6	$243.60	8.573%	$264.4838	$264.48	$264.50	$264.50
Purchase #7	$149.30	13.603%	$169.6093	$169.61	$169.60	$169.60
7 purchase totals =	$1,054.49		$1,145.1290	$1,145.14	$1,145.15	$1,145.20