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	$102.76	6.827%	$109.7754	$109.78	$109.80	$109.80
Purchase #2	$45.46	10.868%	$50.4006	$50.40	$50.40	$50.40
Purchase #3	$80.68	10.456%	$89.1159	$89.12	$89.10	$89.10
Purchase #4	$191.87	8.337%	$207.8662	$207.87	$207.85	$207.90
Purchase #5	$181.95	7.722%	$196.0002	$196.00	$196.00	$196.00
Purchase #6	$195.61	12.337%	$219.7424	$219.74	$219.75	$219.70
Purchase #7	$180.34	7.573%	$193.9971	$194.00	$194.00	$194.00
7 purchase totals =	$978.67		$1,066.8978	$1,066.91	$1,066.90	$1,066.90