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	$91.39	8.375%	$99.0439	$99.04	$99.05	$99.00
Purchase #2	$74.40	4.679%	$77.8812	$77.88	$77.90	$77.90
Purchase #3	$78.59	10.114%	$86.5386	$86.54	$86.55	$86.50
Purchase #4	$39.50	8.813%	$42.9811	$42.98	$43.00	$43.00
Purchase #5	$120.34	9.724%	$132.0419	$132.04	$132.05	$132.00
Purchase #6	$233.56	7.183%	$250.3366	$250.34	$250.35	$250.30
Purchase #7	$58.50	8.398%	$63.4128	$63.41	$63.40	$63.40
7 purchase totals =	$696.28		$752.2361	$752.23	$752.30	$752.10