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	$147.59	5.464%	$155.6543	$155.65	$155.65	$155.70
Purchase #2	$197.30	6.213%	$209.5582	$209.56	$209.55	$209.60
Purchase #3	$50.56	12.372%	$56.8153	$56.82	$56.80	$56.80
Purchase #4	$136.28	10.872%	$151.0964	$151.10	$151.10	$151.10
Purchase #5	$120.81	8.815%	$131.4594	$131.46	$131.45	$131.50
Purchase #6	$228.89	5.131%	$240.6343	$240.63	$240.65	$240.60
Purchase #7	$96.82	8.228%	$104.7863	$104.79	$104.80	$104.80
7 purchase totals =	$978.25		$1,050.0042	$1,050.01	$1,050.00	$1,050.10