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	$185.30	11.560%	$206.7207	$206.72	$206.70	$206.70
Purchase #2	$167.64	13.104%	$189.6075	$189.61	$189.60	$189.60
Purchase #3	$176.69	3.582%	$183.019	$183.02	$183.00	$183.00
Purchase #4	$165.36	5.621%	$174.6549	$174.65	$174.65	$174.70
Purchase #5	$85.34	4.492%	$89.1735	$89.17	$89.15	$89.20
Purchase #6	$38.26	10.436%	$42.2528	$42.25	$42.25	$42.30
Purchase #7	$52.30	8.188%	$56.5823	$56.58	$56.60	$56.60
7 purchase totals =	$870.89		$942.0107	$942.00	$941.95	$942.10