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	$54.97	12.432%	$61.8039	$61.80	$61.80	$61.80
Purchase #2	$88.82	13.104%	$100.459	$100.46	$100.45	$100.50
Purchase #3	$137.28	8.520%	$148.9763	$148.98	$149.00	$149.00
Purchase #4	$85.33	13.515%	$96.8623	$96.86	$96.85	$96.90
Purchase #5	$84.90	12.204%	$95.2612	$95.26	$95.25	$95.30
Purchase #6	$191.93	13.808%	$218.4317	$218.43	$218.45	$218.40
Purchase #7	$94.72	11.274%	$105.3987	$105.40	$105.40	$105.40
7 purchase totals =	$737.95		$827.1931	$827.19	$827.20	$827.30