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	$97.67	11.851%	$109.2449	$109.24	$109.25	$109.20
Purchase #2	$205.63	4.603%	$215.0951	$215.10	$215.10	$215.10
Purchase #3	$166.32	5.414%	$175.3246	$175.32	$175.30	$175.30
Purchase #4	$103.76	4.155%	$108.0712	$108.07	$108.05	$108.10
Purchase #5	$83.32	6.349%	$88.61	$88.61	$88.60	$88.60
Purchase #6	$163.83	4.658%	$171.4612	$171.46	$171.45	$171.50
Purchase #7	$159.55	9.705%	$175.0343	$175.03	$175.05	$175.00
7 purchase totals =	$980.08		$1,042.8413	$1,042.83	$1,042.80	$1,042.80