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	$75.34	9.195%	$82.2675	$82.27	$82.25	$82.30
Purchase #2	$95.32	9.658%	$104.526	$104.53	$104.55	$104.50
Purchase #3	$73.80	8.292%	$79.9195	$79.92	$79.90	$79.90
Purchase #4	$80.63	6.483%	$85.8572	$85.86	$85.85	$85.90
Purchase #5	$110.69	7.609%	$119.1124	$119.11	$119.10	$119.10
Purchase #6	$215.33	13.682%	$244.7915	$244.79	$244.80	$244.80
Purchase #7	$159.61	11.565%	$178.0689	$178.07	$178.05	$178.10
7 purchase totals =	$810.72		$894.5430	$894.55	$894.50	$894.60