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	$103.55	10.251%	$114.1649	$114.16	$114.15	$114.20
Purchase #2	$174.76	12.199%	$196.079	$196.08	$196.10	$196.10
Purchase #3	$14.89	11.476%	$16.5988	$16.60	$16.60	$16.60
Purchase #4	$25.62	5.384%	$26.9994	$27.00	$27.00	$27.00
Purchase #5	$124.40	3.393%	$128.6209	$128.62	$128.60	$128.60
Purchase #6	$90.29	10.412%	$99.691	$99.69	$99.70	$99.70
Purchase #7	$68.87	4.597%	$72.036	$72.04	$72.05	$72.00
7 purchase totals =	$602.38		$654.1900	$654.19	$654.20	$654.20