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	$68.34	5.710%	$72.2422	$72.24	$72.25	$72.20
Purchase #2	$174.25	13.673%	$198.0752	$198.08	$198.10	$198.10
Purchase #3	$152.52	4.666%	$159.6366	$159.64	$159.65	$159.60
Purchase #4	$19.31	5.551%	$20.3819	$20.38	$20.40	$20.40
Purchase #5	$91.42	8.464%	$99.1578	$99.16	$99.15	$99.20
Purchase #6	$89.54	8.330%	$96.9987	$97.00	$97.00	$97.00
Purchase #7	$11.94	5.216%	$12.5628	$12.56	$12.55	$12.60
7 purchase totals =	$607.32		$659.0552	$659.06	$659.10	$659.10