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	$90.47	6.117%	$96.004	$96.00	$96.00	$96.00
Purchase #2	$83.28	4.220%	$86.7944	$86.79	$86.80	$86.80
Purchase #3	$178.59	3.500%	$184.8407	$184.84	$184.85	$184.80
Purchase #4	$50.55	6.676%	$53.9247	$53.92	$53.90	$53.90
Purchase #5	$183.47	9.479%	$200.8611	$200.86	$200.85	$200.90
Purchase #6	$63.47	3.843%	$65.9092	$65.91	$65.90	$65.90
Purchase #7	$81.32	10.798%	$90.1009	$90.10	$90.10	$90.10
7 purchase totals =	$731.15		$778.4350	$778.42	$778.40	$778.40