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	$152.82	6.262%	$162.3896	$162.39	$162.40	$162.40
Purchase #2	$96.70	6.626%	$103.1073	$103.11	$103.10	$103.10
Purchase #3	$191.28	12.566%	$215.3162	$215.32	$215.30	$215.30
Purchase #4	$103.37	5.501%	$109.0564	$109.06	$109.05	$109.10
Purchase #5	$87.90	5.541%	$92.7705	$92.77	$92.75	$92.80
Purchase #6	$186.96	12.310%	$209.9748	$209.97	$209.95	$210.00
Purchase #7	$41.37	3.380%	$42.7683	$42.77	$42.75	$42.80
7 purchase totals =	$860.40		$935.3831	$935.39	$935.30	$935.50