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	$198.29	7.574%	$213.3085	$213.31	$213.30	$213.30
Purchase #2	$56.76	13.645%	$64.5049	$64.50	$64.50	$64.50
Purchase #3	$16.77	9.784%	$18.4108	$18.41	$18.40	$18.40
Purchase #4	$25.38	6.227%	$26.9604	$26.96	$26.95	$27.00
Purchase #5	$100.85	4.416%	$105.3035	$105.30	$105.30	$105.30
Purchase #6	$72.33	8.515%	$78.4889	$78.49	$78.50	$78.50
Purchase #7	$199.38	12.270%	$223.8439	$223.84	$223.85	$223.80
7 purchase totals =	$669.76		$730.8209	$730.81	$730.80	$730.80