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	$183.40	8.684%	$199.3265	$199.33	$199.35	$199.30
Purchase #2	$28.73	9.836%	$31.5559	$31.56	$31.55	$31.60
Purchase #3	$204.49	10.737%	$226.4461	$226.45	$226.45	$226.40
Purchase #4	$200.63	7.796%	$216.2711	$216.27	$216.25	$216.30
Purchase #5	$240.87	6.405%	$256.2977	$256.30	$256.30	$256.30
Purchase #6	$171.61	4.495%	$179.3239	$179.32	$179.30	$179.30
Purchase #7	$31.54	6.379%	$33.5519	$33.55	$33.55	$33.60
7 purchase totals =	$1,061.27		$1,142.7731	$1,142.78	$1,142.75	$1,142.80