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	$39.91	4.633%	$41.759	$41.76	$41.75	$41.80
Purchase #2	$33.30	5.816%	$35.2367	$35.24	$35.25	$35.20
Purchase #3	$127.93	11.194%	$142.2505	$142.25	$142.25	$142.30
Purchase #4	$106.85	9.873%	$117.3993	$117.40	$117.40	$117.40
Purchase #5	$131.59	10.859%	$145.8794	$145.88	$145.90	$145.90
Purchase #6	$142.36	7.334%	$152.8007	$152.80	$152.80	$152.80
Purchase #7	$208.65	6.109%	$221.3964	$221.40	$221.40	$221.40
7 purchase totals =	$790.59		$856.7220	$856.73	$856.75	$856.80