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	$7.53	3.104%	$7.7637	$7.76	$7.75	$7.80
Purchase #2	$55.68	9.734%	$61.0999	$61.10	$61.10	$61.10
Purchase #3	$53.56	6.585%	$57.0869	$57.09	$57.10	$57.10
Purchase #4	$102.45	6.578%	$109.1892	$109.19	$109.20	$109.20
Purchase #5	$148.41	12.256%	$166.5991	$166.60	$166.60	$166.60
Purchase #6	$42.63	7.378%	$45.7752	$45.78	$45.80	$45.80
Purchase #7	$57.84	3.470%	$59.847	$59.85	$59.85	$59.80
7 purchase totals =	$468.10		$507.3610	$507.37	$507.40	$507.40