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	$61.33	5.750%	$64.8565	$64.86	$64.85	$64.90
Purchase #2	$97.31	5.207%	$102.3769	$102.38	$102.40	$102.40
Purchase #3	$227.89	3.742%	$236.4176	$236.42	$236.40	$236.40
Purchase #4	$215.42	3.541%	$223.048	$223.05	$223.05	$223.00
Purchase #5	$70.38	13.500%	$79.8813	$79.88	$79.90	$79.90
Purchase #6	$185.50	12.845%	$209.3275	$209.33	$209.35	$209.30
Purchase #7	$78.47	13.494%	$89.0587	$89.06	$89.05	$89.10
7 purchase totals =	$936.30		$1,004.9665	$1,004.98	$1,005.00	$1,005.00