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	$101.61	11.157%	$112.9466	$112.95	$112.95	$112.90
Purchase #2	$233.85	9.181%	$255.3198	$255.32	$255.30	$255.30
Purchase #3	$89.28	3.659%	$92.5468	$92.55	$92.55	$92.50
Purchase #4	$151.74	5.663%	$160.333	$160.33	$160.35	$160.30
Purchase #5	$91.61	4.856%	$96.0586	$96.06	$96.05	$96.10
Purchase #6	$50.42	13.135%	$57.0427	$57.04	$57.05	$57.00
Purchase #7	$43.98	6.512%	$46.844	$46.84	$46.85	$46.80
7 purchase totals =	$762.49		$821.0915	$821.09	$821.10	$820.90