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	$63.51	13.481%	$72.0718	$72.07	$72.05	$72.10
Purchase #2	$92.88	5.615%	$98.0952	$98.10	$98.10	$98.10
Purchase #3	$87.76	4.809%	$91.9804	$91.98	$92.00	$92.00
Purchase #4	$81.65	9.481%	$89.3912	$89.39	$89.40	$89.40
Purchase #5	$49.30	7.645%	$53.069	$53.07	$53.05	$53.10
Purchase #6	$243.28	10.443%	$268.6857	$268.69	$268.70	$268.70
Purchase #7	$46.67	10.850%	$51.7337	$51.73	$51.75	$51.70
7 purchase totals =	$665.05		$725.0270	$725.03	$725.05	$725.10