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	$129.61	9.218%	$141.5574	$141.56	$141.55	$141.60
Purchase #2	$209.83	8.591%	$227.8565	$227.86	$227.85	$227.90
Purchase #3	$113.91	3.525%	$117.9253	$117.93	$117.95	$117.90
Purchase #4	$164.73	6.731%	$175.818	$175.82	$175.80	$175.80
Purchase #5	$185.73	7.834%	$200.2801	$200.28	$200.30	$200.30
Purchase #6	$169.65	9.474%	$185.7226	$185.72	$185.70	$185.70
Purchase #7	$178.76	7.623%	$192.3869	$192.39	$192.40	$192.40
7 purchase totals =	$1,152.22		$1,241.5468	$1,241.56	$1,241.55	$1,241.60