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	$172.52	7.658%	$185.7316	$185.73	$185.75	$185.70
Purchase #2	$154.38	6.175%	$163.913	$163.91	$163.90	$163.90
Purchase #3	$219.32	6.540%	$233.6635	$233.66	$233.65	$233.70
Purchase #4	$81.33	6.759%	$86.8271	$86.83	$86.85	$86.80
Purchase #5	$177.63	7.825%	$191.5295	$191.53	$191.55	$191.50
Purchase #6	$162.96	11.550%	$181.7819	$181.78	$181.80	$181.80
Purchase #7	$55.26	3.655%	$57.2798	$57.28	$57.30	$57.30
7 purchase totals =	$1,023.40		$1,100.7264	$1,100.72	$1,100.80	$1,100.70