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	$149.30	10.346%	$164.7466	$164.75	$164.75	$164.70
Purchase #2	$94.36	5.835%	$99.8659	$99.87	$99.85	$99.90
Purchase #3	$184.31	10.490%	$203.6441	$203.64	$203.65	$203.60
Purchase #4	$187.40	13.676%	$213.0288	$213.03	$213.05	$213.00
Purchase #5	$31.91	5.175%	$33.5613	$33.56	$33.55	$33.60
Purchase #6	$169.56	10.850%	$187.9573	$187.96	$187.95	$188.00
Purchase #7	$53.81	10.412%	$59.4127	$59.41	$59.40	$59.40
7 purchase totals =	$870.65		$962.2167	$962.22	$962.20	$962.20