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	$40.75	9.104%	$44.4599	$44.46	$44.45	$44.50
Purchase #2	$70.42	11.745%	$78.6908	$78.69	$78.70	$78.70
Purchase #3	$202.98	4.543%	$212.2014	$212.20	$212.20	$212.20
Purchase #4	$176.33	11.330%	$196.3082	$196.31	$196.30	$196.30
Purchase #5	$98.58	7.808%	$106.2771	$106.28	$106.30	$106.30
Purchase #6	$232.51	7.578%	$250.1296	$250.13	$250.15	$250.10
Purchase #7	$88.90	10.671%	$98.3865	$98.39	$98.40	$98.40
7 purchase totals =	$910.47		$986.4535	$986.46	$986.50	$986.50