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	$78.31	9.197%	$85.5122	$85.51	$85.50	$85.50
Purchase #2	$141.62	7.242%	$151.8761	$151.88	$151.90	$151.90
Purchase #3	$55.59	10.744%	$61.5626	$61.56	$61.55	$61.60
Purchase #4	$27.80	12.133%	$31.173	$31.17	$31.15	$31.20
Purchase #5	$245.71	5.688%	$259.686	$259.69	$259.70	$259.70
Purchase #6	$84.92	13.515%	$96.3969	$96.40	$96.40	$96.40
Purchase #7	$250.58	7.542%	$269.4787	$269.48	$269.50	$269.50
7 purchase totals =	$884.53		$955.6855	$955.69	$955.70	$955.80