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	$91.76	4.799%	$96.1636	$96.16	$96.15	$96.20
Purchase #2	$148.39	9.600%	$162.6354	$162.64	$162.65	$162.60
Purchase #3	$226.49	6.829%	$241.957	$241.96	$241.95	$242.00
Purchase #4	$105.70	3.675%	$109.5845	$109.58	$109.60	$109.60
Purchase #5	$102.39	3.224%	$105.6911	$105.69	$105.70	$105.70
Purchase #6	$122.61	9.195%	$133.884	$133.88	$133.90	$133.90
Purchase #7	$134.60	11.700%	$150.3482	$150.35	$150.35	$150.30
7 purchase totals =	$931.94		$1,000.2638	$1,000.26	$1,000.30	$1,000.30