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	$147.40	4.185%	$153.5687	$153.57	$153.55	$153.60
Purchase #2	$147.35	10.409%	$162.6877	$162.69	$162.70	$162.70
Purchase #3	$96.37	4.424%	$100.6334	$100.63	$100.65	$100.60
Purchase #4	$120.95	7.103%	$129.5411	$129.54	$129.55	$129.50
Purchase #5	$39.72	10.384%	$43.8445	$43.84	$43.85	$43.80
Purchase #6	$214.99	6.283%	$228.4978	$228.50	$228.50	$228.50
Purchase #7	$101.44	8.277%	$109.8362	$109.84	$109.85	$109.80
7 purchase totals =	$868.22		$928.6094	$928.61	$928.65	$928.50