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	$165.97	10.508%	$183.4101	$183.41	$183.40	$183.40
Purchase #2	$200.89	10.639%	$222.2627	$222.26	$222.25	$222.30
Purchase #3	$96.47	3.715%	$100.0539	$100.05	$100.05	$100.10
Purchase #4	$91.69	6.444%	$97.5985	$97.60	$97.60	$97.60
Purchase #5	$61.53	4.113%	$64.0607	$64.06	$64.05	$64.10
Purchase #6	$171.76	7.721%	$185.0216	$185.02	$185.00	$185.00
Purchase #7	$227.97	13.243%	$258.1601	$258.16	$258.15	$258.20
7 purchase totals =	$1,016.28		$1,110.5676	$1,110.56	$1,110.50	$1,110.70