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	$227.90	6.773%	$243.3357	$243.34	$243.35	$243.30
Purchase #2	$171.85	5.482%	$181.2708	$181.27	$181.25	$181.30
Purchase #3	$238.64	12.538%	$268.5607	$268.56	$268.55	$268.60
Purchase #4	$165.97	13.788%	$188.8539	$188.85	$188.85	$188.90
Purchase #5	$41.89	7.507%	$45.0347	$45.03	$45.05	$45.00
Purchase #6	$205.55	6.449%	$218.8059	$218.81	$218.80	$218.80
Purchase #7	$195.96	11.539%	$218.5718	$218.57	$218.55	$218.60
7 purchase totals =	$1,247.76		$1,364.4335	$1,364.43	$1,364.40	$1,364.50