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	$182.48	9.840%	$200.436	$200.44	$200.45	$200.40
Purchase #2	$164.91	8.740%	$179.3231	$179.32	$179.30	$179.30
Purchase #3	$97.75	3.242%	$100.9191	$100.92	$100.90	$100.90
Purchase #4	$82.56	9.798%	$90.6492	$90.65	$90.65	$90.60
Purchase #5	$92.63	6.739%	$98.8723	$98.87	$98.85	$98.90
Purchase #6	$91.93	4.586%	$96.1459	$96.15	$96.15	$96.10
Purchase #7	$84.70	9.650%	$92.8736	$92.87	$92.85	$92.90
7 purchase totals =	$796.96		$859.2192	$859.22	$859.15	$859.10