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	$168.88	3.552%	$174.8786	$174.88	$174.90	$174.90
Purchase #2	$187.36	3.443%	$193.8108	$193.81	$193.80	$193.80
Purchase #3	$189.87	5.121%	$199.5932	$199.59	$199.60	$199.60
Purchase #4	$235.89	9.824%	$259.0638	$259.06	$259.05	$259.10
Purchase #5	$17.52	12.725%	$19.7494	$19.75	$19.75	$19.70
Purchase #6	$165.59	9.443%	$181.2267	$181.23	$181.25	$181.20
Purchase #7	$53.44	8.380%	$57.9183	$57.92	$57.90	$57.90
7 purchase totals =	$1,018.55		$1,086.2408	$1,086.24	$1,086.25	$1,086.20