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	$142.78	6.362%	$151.8637	$151.86	$151.85	$151.90
Purchase #2	$170.29	10.597%	$188.3356	$188.34	$188.35	$188.30
Purchase #3	$65.98	6.196%	$70.0681	$70.07	$70.05	$70.10
Purchase #4	$207.45	3.832%	$215.3995	$215.40	$215.40	$215.40
Purchase #5	$239.97	5.449%	$253.046	$253.05	$253.05	$253.00
Purchase #6	$56.73	4.753%	$59.4264	$59.43	$59.45	$59.40
Purchase #7	$244.73	9.644%	$268.3318	$268.33	$268.35	$268.30
7 purchase totals =	$1,127.93		$1,206.4711	$1,206.48	$1,206.50	$1,206.40