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	$142.52	11.617%	$159.0765	$159.08	$159.10	$159.10
Purchase #2	$36.81	9.350%	$40.2517	$40.25	$40.25	$40.30
Purchase #3	$83.69	6.345%	$89.0001	$89.00	$89.00	$89.00
Purchase #4	$112.31	9.812%	$123.3299	$123.33	$123.35	$123.30
Purchase #5	$218.54	12.589%	$246.052	$246.05	$246.05	$246.10
Purchase #6	$180.73	11.375%	$201.288	$201.29	$201.30	$201.30
Purchase #7	$249.26	4.857%	$261.3666	$261.37	$261.35	$261.40
7 purchase totals =	$1,023.86		$1,120.3648	$1,120.37	$1,120.40	$1,120.50