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	$49.47	5.721%	$52.3002	$52.30	$52.30	$52.30
Purchase #2	$156.76	5.414%	$165.247	$165.25	$165.25	$165.20
Purchase #3	$100.57	8.783%	$109.4031	$109.40	$109.40	$109.40
Purchase #4	$128.73	7.677%	$138.6126	$138.61	$138.60	$138.60
Purchase #5	$185.33	8.119%	$200.3769	$200.38	$200.40	$200.40
Purchase #6	$214.55	8.645%	$233.0978	$233.10	$233.10	$233.10
Purchase #7	$175.47	6.344%	$186.6018	$186.60	$186.60	$186.60
7 purchase totals =	$1,010.88		$1,085.6394	$1,085.64	$1,085.65	$1,085.60