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	$189.31	4.772%	$198.3439	$198.34	$198.35	$198.30
Purchase #2	$6.50	4.208%	$6.7735	$6.77	$6.75	$6.80
Purchase #3	$239.94	12.229%	$269.2823	$269.28	$269.30	$269.30
Purchase #4	$43.59	3.870%	$45.2769	$45.28	$45.30	$45.30
Purchase #5	$41.60	11.713%	$46.4726	$46.47	$46.45	$46.50
Purchase #6	$158.37	5.514%	$167.1025	$167.10	$167.10	$167.10
Purchase #7	$123.97	3.657%	$128.5036	$128.50	$128.50	$128.50
7 purchase totals =	$803.28		$861.7553	$861.74	$861.75	$861.80