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	$223.62	9.809%	$245.5549	$245.55	$245.55	$245.60
Purchase #2	$39.46	7.256%	$42.3232	$42.32	$42.30	$42.30
Purchase #3	$56.47	4.171%	$58.8254	$58.83	$58.85	$58.80
Purchase #4	$165.78	3.603%	$171.7531	$171.75	$171.75	$171.80
Purchase #5	$99.76	13.403%	$113.1308	$113.13	$113.15	$113.10
Purchase #6	$131.45	7.607%	$141.4494	$141.45	$141.45	$141.40
Purchase #7	$241.26	9.699%	$264.6598	$264.66	$264.65	$264.70
7 purchase totals =	$957.80		$1,037.6966	$1,037.69	$1,037.70	$1,037.70