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	$187.60	11.727%	$209.5999	$209.60	$209.60	$209.60
Purchase #2	$150.35	12.273%	$168.8025	$168.80	$168.80	$168.80
Purchase #3	$81.47	11.764%	$91.0541	$91.05	$91.05	$91.10
Purchase #4	$227.89	6.754%	$243.2817	$243.28	$243.30	$243.30
Purchase #5	$148.46	9.156%	$162.053	$162.05	$162.05	$162.10
Purchase #6	$19.75	3.465%	$20.4343	$20.43	$20.45	$20.40
Purchase #7	$186.65	5.357%	$196.6488	$196.65	$196.65	$196.60
7 purchase totals =	$1,002.17		$1,091.8743	$1,091.86	$1,091.90	$1,091.90