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	$193.54	3.137%	$199.6113	$199.61	$199.60	$199.60
Purchase #2	$84.47	12.270%	$94.8345	$94.83	$94.85	$94.80
Purchase #3	$243.41	10.834%	$269.781	$269.78	$269.80	$269.80
Purchase #4	$196.67	4.147%	$204.8259	$204.83	$204.85	$204.80
Purchase #5	$182.76	3.740%	$189.5952	$189.60	$189.60	$189.60
Purchase #6	$187.64	13.140%	$212.2959	$212.30	$212.30	$212.30
Purchase #7	$144.36	12.828%	$162.8785	$162.88	$162.90	$162.90
7 purchase totals =	$1,232.85		$1,333.8223	$1,333.83	$1,333.90	$1,333.80