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	$7.66	5.232%	$8.0608	$8.06	$8.05	$8.10
Purchase #2	$58.57	12.525%	$65.9059	$65.91	$65.90	$65.90
Purchase #3	$250.31	5.242%	$263.4313	$263.43	$263.45	$263.40
Purchase #4	$91.58	5.218%	$96.3586	$96.36	$96.35	$96.40
Purchase #5	$63.68	13.765%	$72.4456	$72.45	$72.45	$72.40
Purchase #6	$123.46	10.849%	$136.8542	$136.85	$136.85	$136.90
Purchase #7	$86.44	3.143%	$89.1568	$89.16	$89.15	$89.20
7 purchase totals =	$681.70		$732.2132	$732.22	$732.20	$732.30