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	$102.99	4.542%	$107.6678	$107.67	$107.65	$107.70
Purchase #2	$125.29	13.830%	$142.6176	$142.62	$142.60	$142.60
Purchase #3	$179.93	3.790%	$186.7493	$186.75	$186.75	$186.70
Purchase #4	$235.66	6.326%	$250.5679	$250.57	$250.55	$250.60
Purchase #5	$41.75	4.846%	$43.7732	$43.77	$43.75	$43.80
Purchase #6	$100.77	10.777%	$111.63	$111.63	$111.65	$111.60
Purchase #7	$140.28	13.281%	$158.9106	$158.91	$158.90	$158.90
7 purchase totals =	$926.67		$1,001.9164	$1,001.92	$1,001.85	$1,001.90