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	$49.33	10.436%	$54.4781	$54.48	$54.50	$54.50
Purchase #2	$168.41	3.688%	$174.621	$174.62	$174.60	$174.60
Purchase #3	$213.45	11.549%	$238.1013	$238.10	$238.10	$238.10
Purchase #4	$184.61	6.501%	$196.6115	$196.61	$196.60	$196.60
Purchase #5	$157.32	6.317%	$167.2579	$167.26	$167.25	$167.30
Purchase #6	$85.32	7.510%	$91.7275	$91.73	$91.75	$91.70
Purchase #7	$167.75	8.566%	$182.1195	$182.12	$182.10	$182.10
7 purchase totals =	$1,026.19		$1,104.9168	$1,104.92	$1,104.90	$1,104.90