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	$55.44	11.275%	$61.6909	$61.69	$61.70	$61.70
Purchase #2	$156.67	6.797%	$167.3189	$167.32	$167.30	$167.30
Purchase #3	$93.33	3.653%	$96.7393	$96.74	$96.75	$96.70
Purchase #4	$210.96	8.766%	$229.4528	$229.45	$229.45	$229.50
Purchase #5	$157.31	7.827%	$169.6227	$169.62	$169.60	$169.60
Purchase #6	$178.78	4.685%	$187.1558	$187.16	$187.15	$187.20
Purchase #7	$83.80	8.413%	$90.8501	$90.85	$90.85	$90.90
7 purchase totals =	$936.29		$1,002.8305	$1,002.83	$1,002.80	$1,002.90