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	$152.39	7.705%	$164.1316	$164.13	$164.15	$164.10
Purchase #2	$235.77	10.839%	$261.3251	$261.33	$261.35	$261.30
Purchase #3	$108.54	11.532%	$121.0568	$121.06	$121.05	$121.10
Purchase #4	$167.68	7.414%	$180.1118	$180.11	$180.10	$180.10
Purchase #5	$99.42	6.238%	$105.6218	$105.62	$105.60	$105.60
Purchase #6	$86.52	6.293%	$91.9647	$91.96	$91.95	$92.00
Purchase #7	$73.27	13.801%	$83.382	$83.38	$83.40	$83.40
7 purchase totals =	$923.59		$1,007.5938	$1,007.59	$1,007.60	$1,007.60