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	$32.40	4.421%	$33.8324	$33.83	$33.85	$33.80
Purchase #2	$171.58	11.544%	$191.3872	$191.39	$191.40	$191.40
Purchase #3	$233.46	10.807%	$258.69	$258.69	$258.70	$258.70
Purchase #4	$110.47	8.819%	$120.2123	$120.21	$120.20	$120.20
Purchase #5	$98.93	6.351%	$105.213	$105.21	$105.20	$105.20
Purchase #6	$61.27	10.474%	$67.6874	$67.69	$67.70	$67.70
Purchase #7	$234.37	3.261%	$242.0128	$242.01	$242.00	$242.00
7 purchase totals =	$942.48		$1,019.0351	$1,019.03	$1,019.05	$1,019.00