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	$137.66	4.744%	$144.1906	$144.19	$144.20	$144.20
Purchase #2	$68.82	4.346%	$71.8109	$71.81	$71.80	$71.80
Purchase #3	$180.64	8.850%	$196.6266	$196.63	$196.65	$196.60
Purchase #4	$127.96	11.674%	$142.8981	$142.90	$142.90	$142.90
Purchase #5	$178.87	9.287%	$195.4817	$195.48	$195.50	$195.50
Purchase #6	$109.31	4.610%	$114.3492	$114.35	$114.35	$114.30
Purchase #7	$146.91	5.675%	$155.2471	$155.25	$155.25	$155.20
7 purchase totals =	$950.17		$1,020.6042	$1,020.61	$1,020.65	$1,020.50