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	$76.56	8.123%	$82.779	$82.78	$82.80	$82.80
Purchase #2	$52.26	13.807%	$59.4755	$59.48	$59.50	$59.50
Purchase #3	$170.49	12.476%	$191.7603	$191.76	$191.75	$191.80
Purchase #4	$120.29	8.122%	$130.06	$130.06	$130.05	$130.10
Purchase #5	$187.46	13.844%	$213.412	$213.41	$213.40	$213.40
Purchase #6	$179.27	11.481%	$199.852	$199.85	$199.85	$199.90
Purchase #7	$80.66	10.607%	$89.2156	$89.22	$89.20	$89.20
7 purchase totals =	$866.99		$966.5544	$966.56	$966.55	$966.70