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	$101.43	11.610%	$113.206	$113.21	$113.20	$113.20
Purchase #2	$79.35	13.720%	$90.2368	$90.24	$90.25	$90.20
Purchase #3	$173.59	3.766%	$180.1274	$180.13	$180.15	$180.10
Purchase #4	$233.53	13.621%	$265.3391	$265.34	$265.35	$265.30
Purchase #5	$36.42	5.474%	$38.4136	$38.41	$38.40	$38.40
Purchase #6	$95.73	7.829%	$103.2247	$103.22	$103.20	$103.20
Purchase #7	$232.69	11.627%	$259.7449	$259.74	$259.75	$259.70
7 purchase totals =	$952.74		$1,050.2925	$1,050.29	$1,050.30	$1,050.10