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	$41.56	4.790%	$43.5507	$43.55	$43.55	$43.60
Purchase #2	$176.65	6.836%	$188.7258	$188.73	$188.75	$188.70
Purchase #3	$242.38	12.391%	$272.4133	$272.41	$272.40	$272.40
Purchase #4	$108.47	9.316%	$118.5751	$118.58	$118.60	$118.60
Purchase #5	$242.83	10.736%	$268.9002	$268.90	$268.90	$268.90
Purchase #6	$109.34	4.351%	$114.0974	$114.10	$114.10	$114.10
Purchase #7	$93.54	3.636%	$96.9411	$96.94	$96.95	$96.90
7 purchase totals =	$1,014.77		$1,103.2036	$1,103.21	$1,103.25	$1,103.20