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	$184.39	11.332%	$205.2851	$205.29	$205.30	$205.30
Purchase #2	$85.82	10.562%	$94.8843	$94.88	$94.90	$94.90
Purchase #3	$72.91	12.658%	$82.1389	$82.14	$82.15	$82.10
Purchase #4	$74.31	5.328%	$78.2692	$78.27	$78.25	$78.30
Purchase #5	$142.92	10.258%	$157.5807	$157.58	$157.60	$157.60
Purchase #6	$215.60	4.277%	$224.8212	$224.82	$224.80	$224.80
Purchase #7	$193.42	6.442%	$205.8801	$205.88	$205.90	$205.90
7 purchase totals =	$969.37		$1,048.8595	$1,048.86	$1,048.90	$1,048.90