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	$171.90	5.613%	$181.5487	$181.55	$181.55	$181.50
Purchase #2	$91.61	5.731%	$96.8602	$96.86	$96.85	$96.90
Purchase #3	$145.44	13.531%	$165.1195	$165.12	$165.10	$165.10
Purchase #4	$72.84	11.203%	$81.0003	$81.00	$81.00	$81.00
Purchase #5	$43.28	10.505%	$47.8266	$47.83	$47.85	$47.80
Purchase #6	$233.34	3.425%	$241.3319	$241.33	$241.35	$241.30
Purchase #7	$168.46	13.274%	$190.8214	$190.82	$190.80	$190.80
7 purchase totals =	$926.87		$1,004.5086	$1,004.51	$1,004.50	$1,004.40