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	$133.38	9.180%	$145.6243	$145.62	$145.60	$145.60
Purchase #2	$157.43	10.352%	$173.7272	$173.73	$173.75	$173.70
Purchase #3	$181.62	5.232%	$191.1224	$191.12	$191.10	$191.10
Purchase #4	$93.73	3.340%	$96.8606	$96.86	$96.85	$96.90
Purchase #5	$72.43	12.685%	$81.6177	$81.62	$81.60	$81.60
Purchase #6	$185.54	5.639%	$196.0026	$196.00	$196.00	$196.00
Purchase #7	$189.66	13.560%	$215.3779	$215.38	$215.40	$215.40
7 purchase totals =	$1,013.79		$1,100.3327	$1,100.33	$1,100.30	$1,100.30