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	$185.95	4.760%	$194.8012	$194.80	$194.80	$194.80
Purchase #2	$83.95	10.675%	$92.9117	$92.91	$92.90	$92.90
Purchase #3	$174.80	4.874%	$183.3198	$183.32	$183.30	$183.30
Purchase #4	$153.39	5.638%	$162.0381	$162.04	$162.05	$162.00
Purchase #5	$52.41	13.401%	$59.4335	$59.43	$59.45	$59.40
Purchase #6	$51.46	10.410%	$56.817	$56.82	$56.80	$56.80
Purchase #7	$202.61	10.579%	$224.0441	$224.04	$224.05	$224.00
7 purchase totals =	$904.57		$973.3654	$973.36	$973.35	$973.20