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	$100.59	9.814%	$110.4619	$110.46	$110.45	$110.50
Purchase #2	$233.65	7.132%	$250.3139	$250.31	$250.30	$250.30
Purchase #3	$167.90	13.633%	$190.7898	$190.79	$190.80	$190.80
Purchase #4	$169.80	11.608%	$189.5104	$189.51	$189.50	$189.50
Purchase #5	$5.54	10.715%	$6.1336	$6.13	$6.15	$6.10
Purchase #6	$168.32	10.818%	$186.5289	$186.53	$186.55	$186.50
Purchase #7	$246.60	7.170%	$264.2812	$264.28	$264.30	$264.30
7 purchase totals =	$1,092.40		$1,198.0197	$1,198.01	$1,198.05	$1,198.00