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	$127.93	6.710%	$136.5141	$136.51	$136.50	$136.50
Purchase #2	$150.96	6.498%	$160.7694	$160.77	$160.75	$160.80
Purchase #3	$91.62	7.520%	$98.5098	$98.51	$98.50	$98.50
Purchase #4	$105.39	8.460%	$114.306	$114.31	$114.30	$114.30
Purchase #5	$135.37	11.232%	$150.5748	$150.57	$150.55	$150.60
Purchase #6	$202.36	3.813%	$210.076	$210.08	$210.10	$210.10
Purchase #7	$230.26	3.638%	$238.6369	$238.64	$238.65	$238.60
7 purchase totals =	$1,043.89		$1,109.3870	$1,109.39	$1,109.35	$1,109.40