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	$143.40	3.384%	$148.2527	$148.25	$148.25	$148.30
Purchase #2	$211.89	10.560%	$234.2656	$234.27	$234.25	$234.30
Purchase #3	$36.63	3.869%	$38.0472	$38.05	$38.05	$38.00
Purchase #4	$226.32	7.756%	$243.8734	$243.87	$243.85	$243.90
Purchase #5	$63.27	7.171%	$67.8071	$67.81	$67.80	$67.80
Purchase #6	$170.85	10.751%	$189.2181	$189.22	$189.20	$189.20
Purchase #7	$48.50	10.441%	$53.5639	$53.56	$53.55	$53.60
7 purchase totals =	$900.86		$975.0280	$975.03	$974.95	$975.10