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	$194.40	4.109%	$202.3879	$202.39	$202.40	$202.40
Purchase #2	$43.26	5.779%	$45.76	$45.76	$45.75	$45.80
Purchase #3	$239.30	8.519%	$259.686	$259.69	$259.70	$259.70
Purchase #4	$165.33	8.507%	$179.3946	$179.39	$179.40	$179.40
Purchase #5	$170.45	3.270%	$176.0237	$176.02	$176.00	$176.00
Purchase #6	$81.31	9.845%	$89.315	$89.32	$89.30	$89.30
Purchase #7	$47.77	11.424%	$53.2272	$53.23	$53.25	$53.20
7 purchase totals =	$941.82		$1,005.7944	$1,005.80	$1,005.80	$1,005.80