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	$245.94	5.529%	$259.538	$259.54	$259.55	$259.50
Purchase #2	$15.96	10.302%	$17.6042	$17.60	$17.60	$17.60
Purchase #3	$45.59	3.745%	$47.2973	$47.30	$47.30	$47.30
Purchase #4	$179.80	4.483%	$187.8604	$187.86	$187.85	$187.90
Purchase #5	$100.33	3.399%	$103.7402	$103.74	$103.75	$103.70
Purchase #6	$91.35	9.370%	$99.9095	$99.91	$99.90	$99.90
Purchase #7	$45.41	5.416%	$47.8694	$47.87	$47.85	$47.90
7 purchase totals =	$724.38		$763.8190	$763.82	$763.80	$763.80