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	$91.95	7.173%	$98.5456	$98.55	$98.55	$98.50
Purchase #2	$162.89	8.307%	$176.4213	$176.42	$176.40	$176.40
Purchase #3	$37.61	5.261%	$39.5887	$39.59	$39.60	$39.60
Purchase #4	$112.38	7.267%	$120.5467	$120.55	$120.55	$120.50
Purchase #5	$159.39	5.187%	$167.6576	$167.66	$167.65	$167.70
Purchase #6	$174.79	4.136%	$182.0193	$182.02	$182.00	$182.00
Purchase #7	$239.54	7.764%	$258.1379	$258.14	$258.15	$258.10
7 purchase totals =	$978.55		$1,042.9171	$1,042.93	$1,042.90	$1,042.80